[NaCl SDK] make example Makefiles quiet by default

This is a port of some of the changes made to the common.mk
system when it was ported to support building nacltoons.

Also, change oshelpers "rm -f" so that is doesn't output
anything when it can't find files (this matches /bin/rm
behavior).

Also, remove redundant nmf build rules from host_vc.mk and
host_gcc.mk.

Also, add .mk files to exclusion list in top level
PRESUBMIT.py since they contain lines longer than 80 chars
and fixing this would make them harder to read.

BUG=None


Review URL: https://chromiumcodereview.appspot.com/12209097

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@181856 0039d316-1c4b-4281-b951-d872f2087c98
diff --git a/PRESUBMIT.py b/PRESUBMIT.py
index 07674af..751cfb14 100644
--- a/PRESUBMIT.py
+++ b/PRESUBMIT.py
@@ -18,6 +18,7 @@
     r"^breakpad[\\\/].*",
     r"^native_client_sdk[\\\/]src[\\\/]build_tools[\\\/]make_rules.py",
     r"^native_client_sdk[\\\/]src[\\\/]build_tools[\\\/]make_simple.py",
+    r"^native_client_sdk[\\\/]src[\\\/]tools[\\\/].*.mk",
     r"^net[\\\/]tools[\\\/]spdyshark[\\\/].*",
     r"^skia[\\\/].*",
     r"^v8[\\\/].*",