[gtk/more-vs-proj-updates] win32/config-msvc.mak: Improve flexibility

[Chun-wei Fan <fanchunwei src gnome org>]

commit fd2e32ada160f7028cf94b4ed050c47255859b0c
Author: Chun-wei Fan <fanchunwei src gnome org>
Date:   Mon Aug 8 19:32:11 2022 +0800

    win32/config-msvc.mak: Improve flexibility
    
    Allow one to specify INCLUDEDIR and LIBDIR to locate the headers needed
    for generating sources, if they are not under $(PREFIX)\include and
    $(PREFIX)\lib, repsectively.

 win32/config-msvc.mak.in | 24 ++++++++++++++++--------
 1 file changed, 16 insertions(+), 8 deletions(-)
---
diff --git a/win32/config-msvc.mak.in b/win32/config-msvc.mak.in
index 0f19043f1d..c9bb6cf0e4 100644
--- a/win32/config-msvc.mak.in
+++ b/win32/config-msvc.mak.in
@@ -46,6 +46,14 @@ GLIB_COMPILE_SCHEMAS = $(PREFIX)\bin\glib-compile-schemas.exe
 MSGFMT = msgfmt
 !endif
 
+!ifndef INCLUDEDIR
+INCLUDEDIR=$(PREFIX)\include
+!endif
+
+!ifndef LIBDIR
+LIBDIR=$(PREFIX)\lib
+!endif
+
 !if "$(PLAT)" == "x64"
 AT_PLAT=x86_64
 !elseif "$(PLAT)" == "arm64"
@@ -85,14 +93,14 @@ GTK_PREPROCESSOR_FLAGS =    \
         /I.\vs$(VSVER)\$(CFG)\$(PLAT)\obj\gtk-3        \
         /I.\vs$(VSVER)\$(CFG)\$(PLAT)\obj\gdk-3        \
         /I..   \
-        /I$(PREFIX)\include\gdk-pixbuf-2.0     \
-        /I$(PREFIX)\include\pango-1.0  \
-        /I$(PREFIX)\include\atk-1.0    \
-        /I$(PREFIX)\include\harfbuzz   \
-        /I$(PREFIX)\include\cairo      \
-        /I$(PREFIX)\include\gio-win32-2.0      \
-        /I$(PREFIX)\include\glib-2.0   \
-        /I$(PREFIX)\lib\glib-2.0\include       \
+        /I$(INCLUDEDIR)\gdk-pixbuf-2.0 \
+        /I$(INCLUDEDIR)\pango-1.0      \
+        /I$(INCLUDEDIR)\atk-1.0        \
+        /I$(INCLUDEDIR)\harfbuzz       \
+        /I$(INCLUDEDIR)\cairo  \
+        /I$(INCLUDEDIR)\gio-win32-2.0  \
+        /I$(INCLUDEDIR)\glib-2.0       \
+        /I$(LIBDIR)\glib-2.0\include   \
         /I$(PREFIX)\include    \
         /DHAVE_CONFIG_H        \
         /DG_DISABLE_SINGLE_INCLUDES    \