eduke32: convert bmp -> png for gdk-pixbuf-csource

diff --git a/GNUmakefile b/GNUmakefile

index f83f04d..25a4fa8 100644

--- a/GNUmakefile

+++ b/GNUmakefile

@@ -798,6 +798,9 @@ libklzw$(DLLSUFFIX): $(engine_src)/klzw.cpp

 	$(COMPILE_STATUS)

 	$(RECIPE_IF) $(COMPILER_C) -shared -fPIC $< -o $@ $(RECIPE_RESULT_COMPILE)

+%.png: %.bmp

+	gm convert $< $@

+

 # to debug the tools link phase, make a copy of this rule explicitly replacing % with the name of a tool, such as kextract

 %$(EXESUFFIX): $(tools_obj)/%.$o $(foreach i,tools $(tools_deps),$(call expandobjs,$i))

 	$(LINK_STATUS)

@@ -880,7 +883,7 @@ $$($1_obj)/%.$$o: $$($1_rsrc)/%.c | $$($1_obj)

 	$$(call MKDIR,$$(dir $$@))

 	$$(RECIPE_IF) $$(COMPILER_C) $$($1_cflags) -c $$< -o $$@ $$(RECIPE_RESULT_COMPILE)

-$$($1_obj)/%_banner.c: $$($1_rsrc)/%.bmp | $$($1_obj)

+$$($1_obj)/%_banner.c: $$($1_rsrc)/%.png | $$($1_obj)

 	echo "#include \"gtkpixdata_shim.h\"" > $$@

 	gdk-pixbuf-csource --extern --struct --raw --name=startbanner_pixdata $$^ | sed 's/load_inc//' >> $$@

    hash = "sha256-dyZ4JtDBxsTDe9uQDWxJe7M74X7m+5wpEHm+i+s9hwo=";

  };

  patches = [

    # gdk-pixbuf-csource no longer supports bmp so convert to png

    # patch GNUMakefile to use graphicsmagick to convert bmp -> png

    ./convert-bmp-to-png.diff

  ];

  buildInputs = [

    flac

    libvorbis