Ignore more warnings inside clapack and gmp

Change-Id: Ief04961f4a69d66ef03418cbdd233b6a673328eb
diff --git a/debian/clapack.BUILD b/debian/clapack.BUILD
index b839fae..31e127e 100644
--- a/debian/clapack.BUILD
+++ b/debian/clapack.BUILD
@@ -297,6 +297,8 @@
             "-Wno-self-assign",
         ],
         "gcc": [
+            "-Wno-implicit-fallthrough",
+            "-Wno-array-bounds",
             "-Wno-discarded-qualifiers",
             "-Wno-maybe-uninitialized",
             "-Wno-unused-but-set-variable",