Make enums.py c header output resistent to format.sh

Summary:
This PR changes the enums.py to create the header the same as format.sh would layout it. Reduces the clutter due to missed format.sh calls after enums.py generation.
Closes https://github.com/facebook/yoga/pull/380

Reviewed By: gkassabli

Differential Revision: D4529593

Pulled By: emilsjolander

fbshipit-source-id: 7281e0d500f79459c19cc8fe6dbc8fd77f0a537c

format.sh

@@ -2,7 +2,7 @@
 
 BASEDIR="$(dirname "$0")"
 FILES=$(find "$BASEDIR" \( -path "$BASEDIR/buck-out" -o -path "$BASEDIR/lib" \) -prune -o \
-  \( -name  \*.h -o -name \*.c -o -name \*.cpp \) -print)
+  \( -name  \*.h ! -name YGEnums.h -o -name \*.c -o -name \*.cpp \) -print)
 
 for f in $FILES "$@"; do
   clang-format \