we want these macros to be emtpy strings, not 1s

The substituted 1s cause i686-pc-mingw32-windres to bail out with syntax
error in solenv/inc/shlinfo.rc at line 67.

solenv/gbuild/platform/winmingw.mk

@@ -525,9 +525,9 @@ $(call gb_WinResTarget_WinResTarget_init,$(2))
 $(call gb_WinResTarget_add_file,$(2),solenv/inc/shlinfo)
 $(call gb_WinResTarget_set_defs,$(2),\
 		$$(DEFS) \
-		-DADDITIONAL_VERINFO1 \
-		-DADDITIONAL_VERINFO2 \
-		-DADDITIONAL_VERINFO3 \
+		-DADDITIONAL_VERINFO1="" \
+		-DADDITIONAL_VERINFO2="" \
+		-DADDITIONAL_VERINFO3="" \
 )
 $(call gb_Library_add_nativeres,$(1),$(2))
 $(call gb_Library_get_clean_target,$(1)) : $(call gb_WinResTarget_get_clean_target,$(2))