autotools: include meson build files in tarball

This adds the meson.build, meson_options.txt, and a few scripts that are
used exclusively by the meson build.

v2: - Remove accidentally included changes needed to test make dist with
      LLVM > 3.9

Signed-off-by: Dylan Baker <dylan.c.baker@intel.com>
Acked-by: Eric Engestrom <eric@engestrom.ch>
Reviewed-by: Emil Velikov <emil.velikov@collabora.com>

src/util/tests/string_buffer/Makefile.am

@@ -38,3 +38,5 @@ string_buffer_test_LDADD = \
 	$(top_builddir)/src/util/libmesautil.la \
 	$(PTHREAD_LIBS) \
 	$(DLOPEN_LIBS)
+
+EXTRA_DIST = meson.build