build: add config.sub and config.guess to tarballs target

fixes errors ./configure was complaining about

NOTE: This is a candidate for the 9.0 branch.

Reviewed-by: Matt Turner <mattst88@gmail.com>

Makefile.am

@@ -61,6 +61,8 @@ PACKAGE_NAME = MesaLib-$(PACKAGE_VERSION)
 EXTRA_FILES = \
 	aclocal.m4					\
 	configure					\
+	bin/config.sub					\
+	bin/config.guess				\
 	bin/install-sh					\
 	src/glsl/glsl_parser.cc				\
 	src/glsl/glsl_parser.h				\