win32: Fix Makefile.win32 build

The Makefile.win32 build system assumes that the files are in the same
directory level. If this is not the case, the compiler fails when it
tries to write the object files to a non-existing directory.

This can be fixed simply by making sure that the destination directory
always exists.

Fixes:

fatal error C1083: Cannot open compiler generated file:
'release/win32/cairo-win32-debug.obj': No such file or directory

build/Makefile.win32.common

@@ -65,11 +65,11 @@ endif
 # Some generic rules
 
 $(CFG)/%.obj: %.c $(top_srcdir)/src/cairo-features.h
-	@mkdir -p $(CFG)
+	@mkdir -p $(CFG)/`dirname $<`
 	@$(CC) $(CAIRO_CFLAGS) -c -Fo"$@" $<
 
 $(CFG)/%-static.obj: %.c $(top_srcdir)/src/cairo-features.h
-	@mkdir -p $(CFG)
+	@mkdir -p $(CFG)/`dirname $<`
 	@$(CC) $(CAIRO_CFLAGS) -c -DCAIRO_WIN32_STATIC_BUILD=1 -Fo"$@" $<
 
 clean: