[gtkmm/gtkmm-3-24] NMake Makefiles: Mention about the 'prep-git-build' target

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

commit ac32a9cf3b1078fedfa9dea73419a2eabb7e4741
Author: Chun-wei Fan <fanchunwei src gnome org>
Date:   Fri Apr 10 15:42:44 2020 +0800

    NMake Makefiles: Mention about the 'prep-git-build' target
    
    Let people know how it may be used to build from GIT checkouts.

 MSVC_NMake/info-msvc.mak | 4 ++++
 1 file changed, 4 insertions(+)
---
diff --git a/MSVC_NMake/info-msvc.mak b/MSVC_NMake/info-msvc.mak
index 50ef9119..7cef70b7 100644
--- a/MSVC_NMake/info-msvc.mak
+++ b/MSVC_NMake/info-msvc.mak
@@ -56,6 +56,10 @@ help:
        @echo LIBs, along with the introspection files if applicable) to appropriate
        @echo locations under ^$(PREFIX).
        @echo.
+       @echo A 'prep-git-build' target is supported for building from GIT checkouts, which
+       @echo will generate gdkmm.rc, gtkmm.rc, gdkmmconfig.h and gtkmmconfig.h.  Use this target
+       @echo before building any other targets when building from GIT checkouts.
+       @echo.
        @echo A 'tests' target is supported to build the gtkmm's test programs.
        @echo ======
        @echo.