Merge to XFA: Standalone checkout gets buildtools.

Original Review URL: https://codereview.chromium.org/1149623011
TBR=thestig@chromium.org

Review URL: https://codereview.chromium.org/1152523007
diff --git a/.gitignore b/.gitignore
index 91c35f1..93df69f 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,6 +1,7 @@
 /build/Debug
 /build/Release
 /build/gyp
+/buildtools
 /out
 /testing/gmock
 /testing/gtest