[gtkmm] NMake Makefiles: Fix building test programs

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

commit cec60d6f800dfd1d1bf947d3a765615a9dbdd76b
Author: Chun-wei Fan <fanchunwei src gnome org>
Date:   Mon Jun 8 11:28:57 2020 +0800

    NMake Makefiles: Fix building test programs
    
    Make sure we have rules for building the gdk_rgba test program.

 MSVC_NMake/build-rules-msvc.mak | 2 ++
 1 file changed, 2 insertions(+)
---
diff --git a/MSVC_NMake/build-rules-msvc.mak b/MSVC_NMake/build-rules-msvc.mak
index 2ccfb240..3017f336 100644
--- a/MSVC_NMake/build-rules-msvc.mak
+++ b/MSVC_NMake/build-rules-msvc.mak
@@ -119,6 +119,7 @@ vs$(VSVER)\$(CFG)\$(PLAT)\gtkmm4-test-child_widget2.exe: ..\tests\child_widget2\
 vs$(VSVER)\$(CFG)\$(PLAT)\gtkmm4-test-child_widget_managed.exe: ..\tests\child_widget_managed\main.cc
 vs$(VSVER)\$(CFG)\$(PLAT)\gtkmm4-test-delete_cpp_child.exe: ..\tests\delete_cpp_child\main.cc
 vs$(VSVER)\$(CFG)\$(PLAT)\gtkmm4-test-dialog_deletethis.exe: ..\tests\dialog_deletethis\main.cc
+vs$(VSVER)\$(CFG)\$(PLAT)\gtkmm4-test-gdk_rgba.exe: ..\tests\gdk_rgba\main.cc
 vs$(VSVER)\$(CFG)\$(PLAT)\gtkmm4-test-main_with_options.exe: ..\tests\main_with_options\main.cc
 vs$(VSVER)\$(CFG)\$(PLAT)\gtkmm4-test-menu_destruction.exe: ..\tests\menu_destruction\main.cc
 vs$(VSVER)\$(CFG)\$(PLAT)\gtkmm4-test-object_move.exe: ..\tests\object_move\main.cc
@@ -134,6 +135,7 @@ vs$(VSVER)\$(CFG)\$(PLAT)\gtkmm4-test-child_widget2.exe     \
 vs$(VSVER)\$(CFG)\$(PLAT)\gtkmm4-test-child_widget_managed.exe \
 vs$(VSVER)\$(CFG)\$(PLAT)\gtkmm4-test-delete_cpp_child.exe     \
 vs$(VSVER)\$(CFG)\$(PLAT)\gtkmm4-test-dialog_deletethis.exe    \
+vs$(VSVER)\$(CFG)\$(PLAT)\gtkmm4-test-gdk_rgba.exe     \
 vs$(VSVER)\$(CFG)\$(PLAT)\gtkmm4-test-main_with_options.exe    \
 vs$(VSVER)\$(CFG)\$(PLAT)\gtkmm4-test-menu_destruction.exe     \
 vs$(VSVER)\$(CFG)\$(PLAT)\gtkmm4-test-object_move.exe  \