Это, оказывается, было еще в конце 2006-го

Скрипт сборки ниже, хотя с тех пор добавились еще какие-то модули
Может быть, будут unresolved externals, от них надо избавиться

Особонности такие. При сборке harbour.dll в модуле source\rtl\errorsys.prg надо после #include вставить строки:

#ifdef __EXPORT__

PROCEDURE ErrorSys

Errorblock( &( '{|oError| ERRORPROC(oError)}' ) )

Return

#else
...
#endif

ErrorProc - обработчик ошибок minigui

И сама сборка:

@echo off
cls

IF "%mg_bcc%"=="" SET MG_BCC=d:\bcc55
IF "%mg_root%"=="" SET MG_ROOT=d:\minigui
IF "%mg_hrb%"=="" SET MG_HRB=e:\xharbour

SET CLIBFLAGS= -tW -DHB_FM_STATISTICS_OFF -D__WIN32__ -D__EXPORT__ -a8 -OS -O2 -6 -c -I%mg_hrb%\include;%mg_bcc%\include; -d -w3 -DSIMPLEX

IF EXIST %mg_root%\lib\minigui.lib del %mg_root%\lib\minigui.lib

rem goto :link

rem goto :noprint

%mg_hrb%\bin\harbour hbprinter\winprint -i%mg_hrb%\include;%mg_root%\include; -l -n1 -w2 -gc0 -es2 -D__EXPORT__
%mg_hrb%\bin\harbour miniprint\h_miniprint -i%mg_hrb%\include;%mg_root%\include; -l -n1 -w2 -gc0 -es2 -D__EXPORT__

%mg_bcc%\bin\bcc32 %CLIBFLAGS% winprint.c
%mg_bcc%\bin\bcc32 %CLIBFLAGS% h_miniprint.c
%mg_bcc%\bin\bcc32 %CLIBFLAGS% miniprint\c_miniprint.c

:noprint

%mg_hrb%\bin\harbour h_browse h_scrsaver h_error.prg h_ipaddress.prg h_monthcal.prg h_help.prg h_crypt.prg h_status.prg h_tree.prg h_toolbar.prg errorsys.prg h_init.prg h_media.prg h_winapimisc.prg h_slider.prg h_button.prg h_checkbox.prg h_combo.prg h_controlmisc.prg h_datepicker.prg h_editbox.prg h_dialogs.prg h_grid.prg h_windows.prg h_windowsmdi.prg h_image.prg h_imagelist.prg h_label.prg h_listbox.prg h_menu.prg h_msgbox.prg h_frame.prg h_progressbar.prg h_radio.prg h_spinner.prg h_tab.prg h_textbox.prg h_timer.prg h_cursor.prg h_ini.prg h_report.prg h_registry.prg h_font.prg h_hyperlink.prg h_hotkey.prg h_graph.prg h_dialog.prg h_richeditbox.prg h_edit.prg h_edit_ex.prg h_winprop.prg h_socket.prg h_getbox.prg -i%mg_hrb%\include;%mg_root%\include; -l -n1 -w2 -gc0 -es2 -D__EXPORT__

%mg_bcc%\bin\bcc32 %CLIBFLAGS% h_scrsaver.c
%mg_bcc%\bin\bcc32 %CLIBFLAGS% h_edit.c
%mg_bcc%\bin\bcc32 %CLIBFLAGS% h_edit_ex.c
%mg_bcc%\bin\bcc32 %CLIBFLAGS% h_error.c
%mg_bcc%\bin\bcc32 %CLIBFLAGS% h_ipaddress.c
%mg_bcc%\bin\bcc32 %CLIBFLAGS% c_ipaddress.c
%mg_bcc%\bin\bcc32 %CLIBFLAGS% h_monthcal.c
%mg_bcc%\bin\bcc32 %CLIBFLAGS% c_monthcal.c
%mg_bcc%\bin\bcc32 %CLIBFLAGS% h_help.c
%mg_bcc%\bin\bcc32 %CLIBFLAGS% c_help.c
%mg_bcc%\bin\bcc32 %CLIBFLAGS% h_crypt.c
%mg_bcc%\bin\bcc32 %CLIBFLAGS% c_crypt.c
%mg_bcc%\bin\bcc32 %CLIBFLAGS% h_status.c
%mg_bcc%\bin\bcc32 %CLIBFLAGS% c_status.c
%mg_bcc%\bin\bcc32 %CLIBFLAGS% h_tree.c
%mg_bcc%\bin\bcc32 %CLIBFLAGS% c_tree.c
%mg_bcc%\bin\bcc32 %CLIBFLAGS% c_toolbar.c
%mg_bcc%\bin\bcc32 %CLIBFLAGS% h_toolbar.c
%mg_bcc%\bin\bcc32 %CLIBFLAGS% errorsys.c
%mg_bcc%\bin\bcc32 %CLIBFLAGS% h_init.c
%mg_bcc%\bin\bcc32 %CLIBFLAGS% h_media.c
%mg_bcc%\bin\bcc32 %CLIBFLAGS% c_media.c
%mg_bcc%\bin\bcc32 %CLIBFLAGS% h_winapimisc.c
%mg_bcc%\bin\bcc32 %CLIBFLAGS% h_slider.c
%mg_bcc%\bin\bcc32 %CLIBFLAGS% c_button.c
%mg_bcc%\bin\bcc32 %CLIBFLAGS% c_checkbox.c
%mg_bcc%\bin\bcc32 %CLIBFLAGS% c_combo.c
%mg_bcc%\bin\bcc32 %CLIBFLAGS% c_controlmisc.c
%mg_bcc%\bin\bcc32 %CLIBFLAGS% c_datepicker.c
%mg_bcc%\bin\bcc32 %CLIBFLAGS% c_resource.c
%mg_bcc%\bin\bcc32 %CLIBFLAGS% h_cursor.c
%mg_bcc%\bin\bcc32 %CLIBFLAGS% c_cursor.c
%mg_bcc%\bin\bcc32 %CLIBFLAGS% c_ini.c
%mg_bcc%\bin\bcc32 %CLIBFLAGS% h_ini.c
%mg_bcc%\bin\bcc32 %CLIBFLAGS% h_report.c
%mg_bcc%\bin\bcc32 %CLIBFLAGS% h_registry.c
%mg_bcc%\bin\bcc32 %CLIBFLAGS% h_font.c
%mg_bcc%\bin\bcc32 %CLIBFLAGS% c_font.c
%mg_bcc%\bin\bcc32 %CLIBFLAGS% h_hyperlink.c
%mg_bcc%\bin\bcc32 %CLIBFLAGS% c_hyperlink.c
%mg_bcc%\bin\bcc32 %CLIBFLAGS% h_richeditbox.c
%mg_bcc%\bin\bcc32 %CLIBFLAGS% c_richeditbox.c
%mg_bcc%\bin\bcc32 %CLIBFLAGS% c_bitmap.c
%mg_bcc%\bin\bcc32 %CLIBFLAGS% c_dialog.c
%mg_bcc%\bin\bcc32 %CLIBFLAGS% c_imagelist.c
%mg_bcc%\bin\bcc32 %CLIBFLAGS% h_imagelist.c

%mg_bcc%\bin\bcc32 %CLIBFLAGS% c_winxp.c
%mg_bcc%\bin\bcc32 %CLIBFLAGS% c_editbox.c
%mg_bcc%\bin\bcc32 %CLIBFLAGS% c_dialogs.c
%mg_bcc%\bin\bcc32 %CLIBFLAGS% c_grid.c
%mg_bcc%\bin\bcc32 %CLIBFLAGS% c_windows.c
%mg_bcc%\bin\bcc32 %CLIBFLAGS% c_windowsmdi.c
%mg_bcc%\bin\bcc32 %CLIBFLAGS% c_image.c
%mg_bcc%\bin\bcc32 %CLIBFLAGS% c_label.c
%mg_bcc%\bin\bcc32 %CLIBFLAGS% c_listbox.c
%mg_bcc%\bin\bcc32 %CLIBFLAGS% c_menu.c
%mg_bcc%\bin\bcc32 %CLIBFLAGS% c_msgbox.c
%mg_bcc%\bin\bcc32 %CLIBFLAGS% c_frame.c
%mg_bcc%\bin\bcc32 %CLIBFLAGS% c_progressbar.c
%mg_bcc%\bin\bcc32 %CLIBFLAGS% c_radio.c
%mg_bcc%\bin\bcc32 %CLIBFLAGS% c_registry.c
%mg_bcc%\bin\bcc32 %CLIBFLAGS% c_slider.c
%mg_bcc%\bin\bcc32 %CLIBFLAGS% c_spinner.c
%mg_bcc%\bin\bcc32 %CLIBFLAGS% c_tab.c
%mg_bcc%\bin\bcc32 %CLIBFLAGS% c_textbox.c
%mg_bcc%\bin\bcc32 %CLIBFLAGS% c_timer.c
%mg_bcc%\bin\bcc32 %CLIBFLAGS% c_winapimisc.c
%mg_bcc%\bin\bcc32 %CLIBFLAGS% h_button.c
%mg_bcc%\bin\bcc32 %CLIBFLAGS% h_checkbox.c
%mg_bcc%\bin\bcc32 %CLIBFLAGS% h_combo.c
%mg_bcc%\bin\bcc32 %CLIBFLAGS% h_controlmisc.c
%mg_bcc%\bin\bcc32 %CLIBFLAGS% h_datepicker.c
%mg_bcc%\bin\bcc32 %CLIBFLAGS% h_editbox.c
%mg_bcc%\bin\bcc32 %CLIBFLAGS% h_dialogs.c
%mg_bcc%\bin\bcc32 %CLIBFLAGS% h_grid.c
%mg_bcc%\bin\bcc32 %CLIBFLAGS% h_windows.c
%mg_bcc%\bin\bcc32 %CLIBFLAGS% h_windowsmdi.c
%mg_bcc%\bin\bcc32 %CLIBFLAGS% h_image.c
%mg_bcc%\bin\bcc32 %CLIBFLAGS% h_label.c
%mg_bcc%\bin\bcc32 %CLIBFLAGS% h_listbox.c
%mg_bcc%\bin\bcc32 %CLIBFLAGS% h_menu.c
%mg_bcc%\bin\bcc32 %CLIBFLAGS% h_msgbox.c
%mg_bcc%\bin\bcc32 %CLIBFLAGS% h_frame.c
%mg_bcc%\bin\bcc32 %CLIBFLAGS% h_progressbar.c
%mg_bcc%\bin\bcc32 %CLIBFLAGS% h_radio.c
%mg_bcc%\bin\bcc32 %CLIBFLAGS% h_spinner.c
%mg_bcc%\bin\bcc32 %CLIBFLAGS% h_tab.c
%mg_bcc%\bin\bcc32 %CLIBFLAGS% h_textbox.c
%mg_bcc%\bin\bcc32 %CLIBFLAGS% h_timer.c
%mg_bcc%\bin\bcc32 %CLIBFLAGS% c_scrsaver.c
%mg_bcc%\bin\bcc32 %CLIBFLAGS% h_hotkey.c

%mg_bcc%\bin\bcc32 %CLIBFLAGS% c_hotkey.c
%mg_bcc%\bin\bcc32 %CLIBFLAGS% h_graph.c
%mg_bcc%\bin\bcc32 %CLIBFLAGS% c_graph.c
%mg_bcc%\bin\bcc32 %CLIBFLAGS% h_browse.c
%mg_bcc%\bin\bcc32 %CLIBFLAGS% c_browse.c
%mg_bcc%\bin\bcc32 %CLIBFLAGS% h_socket.c
%mg_bcc%\bin\bcc32 %CLIBFLAGS% h_dialog.c
%mg_bcc%\bin\bcc32 %CLIBFLAGS% h_winprop.c
%mg_bcc%\bin\bcc32 %CLIBFLAGS% c_winprop.c
%mg_bcc%\bin\bcc32 %CLIBFLAGS% h_getbox.c
%mg_bcc%\bin\bcc32 %CLIBFLAGS% c_getbox.c

rem %mg_bcc%\bin\tlib /P32 %mg_root%\lib\minigui +h_scrsaver.obj +h_edit.obj +h_edit_ex.obj +h_error.obj +h_ipaddress.obj +c_ipaddress.obj +h_monthcal.obj +c_monthcal.obj +h_help.obj +c_help.obj +h_status.obj +c_status.obj +h_tree.obj +c_tree.obj +h_toolbar.obj +c_toolbar.obj +errorsys.obj +h_init.obj +h_media.obj + c_media.obj +c_resource.obj +h_cursor.obj +c_cursor.obj +h_ini.obj +c_ini.obj +h_report.obj +h_font.obj +c_font.obj +c_hyperlink.obj +h_hyperlink.obj +c_scrsaver.obj +h_hotkey.obj +c_hotkey.obj +h_graph.obj +c_graph.obj +h_richeditbox.obj +c_richeditbox.obj +h_browse.obj +c_browse.obj +h_socket.obj +c_bitmap.obj +c_imagelist.obj +h_imagelist.obj +c_winxp.obj
rem %mg_bcc%\bin\tlib /P32 %mg_root%\lib\minigui +c_crypt.obj +h_crypt.obj +h_winapimisc.obj +h_slider.obj +c_button.obj +c_checkbox.obj +c_combo.obj +c_controlmisc.obj +c_datepicker.obj +c_editbox.obj +c_dialogs.obj +c_grid.obj +c_windows.obj +c_windowsmdi.obj +c_image.obj +c_label.obj +c_listbox.obj +c_menu.obj +c_msgbox.obj +c_frame.obj +c_progressbar.obj +c_radio.obj +c_registry.obj +c_slider.obj +c_spinner.obj +c_tab.obj +c_textbox.obj +c_timer.obj +c_dialog.obj+c_winapimisc +h_button.obj +h_checkbox.obj +h_combo.obj +h_controlmisc.obj +h_datepicker.obj +h_editbox.obj +h_dialogs.obj +h_grid.obj +h_windows.obj +h_windowsmdi.obj +h_image.obj +h_label.obj +h_listbox.obj
rem %mg_bcc%\bin\tlib /P32 %mg_root%\lib\minigui +h_menu.obj +h_msgbox.obj +h_frame.obj +h_progressbar.obj +h_radio.obj +h_spinner.obj +h_tab.obj +h_textbox.obj +h_timer.obj +h_registry.obj +h_dialog.obj +h_winprop.obj +c_winprop.obj +h_getbox.obj +c_getbox.obj

:link

ILINK32 -aa -Tpd -Gn @minidll.lnk >minidll.err
implib minigui.lib minigui.dll

rem IF EXIST %mg_root%\lib\minigui.bak del %mg_root%\lib\minigui.bak

rem del *.obj
rem del h_*.c
del errorsys.c

SET MG_BCC=
SET MG_HRB=
SET MG_ROOT=