Exclude third_party from formatting

third_party dependencies may not follow SwiftShader's style guide, so
they should be excluded. The presence of this check is preventing me
from updating SPIRV-tools in SwiftShader.

Bug: chromium:543704
Change-Id: Ia2d3c804700a02e215c133699a3fc6316a2f8369

pre-commit

diff --git a/pre-commit b/pre-commit
index 92a1229..a919c5e 100755
--- a/pre-commit
+++ b/pre-commit
@@ -15,9 +15,9 @@
 TMPDIR=$(mktemp -d -t gcp-$(date +%Y-%m-%d-%H-%M-%S)-XXXXXXXXXX)
 diffFile=$(mktemp gpc-XXXXXXXXX --tmpdir=$TMPDIR)
 
-# Get every source file that's been added, changed, or modified in the
-# current index.
-FILES=$(git diff --cached --name-only --diff-filter=ACM | grep '\.cpp$\|\.hpp$\|\.h$\|\.c$')
+# Get every non third-party source file that's been added, changed, or modified
+# in the current index.
+FILES=$(git diff --cached --name-only --diff-filter=ACM | grep -v third_party | grep '\.cpp$\|\.hpp$\|\.h$\|\.c$')
 
 # Checkout a copy of current index into TMPDIR. This is necessary so that we
 # only read the versions of files that are being committed, and not any changes