CLEANUP: Update .gitignore

This excludes ar archives from being ignored.
diff --git a/.gitignore b/.gitignore
index 3a760af..f77751a 100644
--- a/.gitignore
+++ b/.gitignore
@@ -31,6 +31,7 @@
 !/reg-tests
 # Reject some generic files
 *.o
+*.a
 *~
 *.rej
 *.orig