libtool doesn't work if compiling with clang.  Need to add --tag=CC
See bug https://bugs.gentoo.org/731010
--- a/xpaintrw/Makefile.am
+++ b/xpaintrw/Makefile.am
@@ -25,7 +25,7 @@
 
 xpaint_DEFINES = $(ARCH_DEFINES) $(EXTRA_DEFINES) $(XAWLIB_DEFINES)
 
-LIBTOOL = /usr/bin/libtool
+LIBTOOL = /usr/bin/libtool --tag=CC
 AM_CFLAGS   = @X_CFLAGS@ @SPECIAL_CFLAGS@ $(xpaint_DEFINES)
 AM_YFLAGS     = -d
 CLEANFILES    =