[gimp/wip/Jehan/fix-native-win-build] icons: fix the native Windows build in CI with autotools.

[Jehan <jehanp src gnome org>]

commit 4004560d7997450d2864bd1260f546f11213ecc3
Author: Jehan <jehan girinstud io>
Date:   Mon Feb 14 19:30:08 2022 +0100

    icons: fix the native Windows build in CI with autotools.
    
    Fixes:
    
    > make[3]: *** No rule to make target '64/dialog-question.png', needed
    > by 'gimp-core-pixbufs.gresource.xml'.  Stop.
    
    It looks like a bug in autotools on Windows because there is no reason
    why it would fail. The missing PNG should be caught by the '64/%.png'
    rule. Anyway after testing, it fixes the gimp-win(32|64)-native CI jobs.

 icons/Color/Makefile.am | 10 ++++++++++
 1 file changed, 10 insertions(+)
---
diff --git a/icons/Color/Makefile.am b/icons/Color/Makefile.am
index be3292e1bd..487ad6b53d 100644
--- a/icons/Color/Makefile.am
+++ b/icons/Color/Makefile.am
@@ -82,6 +82,16 @@ endif
 
 CLEANFILES = $(noinst_DATA)
 
+# This is basically the same rule as the catch all 64/%.png rule above,
+# because somehow the native Windows build fail without it (no problem
+# on cross-build for Windows or native Linux builds). When trying to
+# build gimp-core-pixbufs.gresource.xml, we were getting an error
+# because of "No rule to make target '64/dialog-question.png'".
+# Interestingly, the problem doesn't happen for the other XML, but maybe
+# it's because it's not needed from within icons/Makefile.am.
+64/dialog-question.png: scalable/dialog-question.svg ../../tools/colorsvg2png
+       mkdir -p $(@D) && \
+       $(top_builddir)/tools/colorsvg2png $< $@ $(@D)
 
 gimp-core-pixbufs.gresource.xml: $(CORE_IMAGES) Makefile.am
        $(AM_V_GEN) ( rm -f $@; \