libtool doesn't work if compiling with clang.  Need to add --tag=CC
Also don't hardcode /usr/bin/tool in gentoo prefix
See bug https://bugs.gentoo.org/731010
--- a/configure.ac
+++ b/configure.ac
@@ -17,6 +17,9 @@
 AC_LANG_C
 AM_PROG_AR
 
+dnl search libtool
+AC_PATH_PROG([PROGLIBTOOL], [libtool])
+
 ## basic types
 
 AC_TYPE_INT8_T
--- a/xpaintrw/Makefile.am
+++ b/xpaintrw/Makefile.am
@@ -28,7 +28,7 @@
 
 xpaint_DEFINES = $(ARCH_DEFINES) $(EXTRA_DEFINES) $(XAWLIB_DEFINES)
 
-LIBTOOL = /usr/bin/libtool
+LIBTOOL = @PROGLIBTOOL@ --tag=CC
 AM_CFLAGS   = @X_CFLAGS@ @SPECIAL_CFLAGS@ $(xpaint_DEFINES)
 AM_YFLAGS     = -d
 CLEANFILES    =