src/build: Add getopt to distribution.

Acked-by: Emil Velikov <emil.l.velikov@gmail.com>
diff --git a/src/Makefile.am b/src/Makefile.am
index 75e2a73..9d1580f 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -59,3 +59,5 @@
 	gallium/tests/unit
 endif
 endif
+
+EXTRA_DIST = getopt