[gtkmm/use-dllexport: 25/60] NMake Makefiles: Mention about the 'prep-git-build' target

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

commit c52b0fe5a01746b1dde006c3554cd42f5d62e90d
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 806236f8..096716b5 100644
--- a/MSVC_NMake/info-msvc.mak
+++ b/MSVC_NMake/info-msvc.mak
@@ -59,6 +59,10 @@ 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 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.