weston-build: Fix aclocal error during autogen.sh

This is a fix to the following bug:
https://bugs.freedesktop.org/show_bug.cgi?id=80214

Signed-off-by: Srivardhan Hebbar <sri.hebbar@samsung.com>

m4/.gitignore

@@ -0,0 +1,5 @@
+libtool.m4
+ltoptions.m4
+ltsugar.m4
+ltversion.m4
+lt~obsolete.m4