[amtk/fix-cleaning-nmake] win32/Makefile.am: Remove generated files on 'make maintainer-clean'

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

commit 0155ad5e1f4b5e0b8d15b90a6e8ec869cfb010f7
Author: Chun-wei Fan <fanchunwei src gnome org>
Date:   Thu Apr 30 10:21:11 2020 +0800

    win32/Makefile.am: Remove generated files on 'make maintainer-clean'
    
    config.h.win32, config-msvc.mak and Makefile are all generated from
    template files during the configure stage, so no need to keep them
    after performing a maintainer-clean.

 win32/Makefile.am | 5 +++++
 1 file changed, 5 insertions(+)
---
diff --git a/win32/Makefile.am b/win32/Makefile.am
index ec6f371..7923061 100644
--- a/win32/Makefile.am
+++ b/win32/Makefile.am
@@ -16,3 +16,8 @@ EXTRA_DIST = \
        pc_base.py              \
        README.txt              \
        replace.py
+
+MAINTAINERCLEANFILES = \
+       config.h.win32  \
+       config-msvc.mak \
+       Makefile