Use LOCAL_CLANG := false for GLES wrappers for now

GLES wrappers built with clang currently result in crashes in libhwui,
UI doesn't come up.

Force gcc for the wrappers until this is investigated and fixed
properly.

Bug: 18003438
Change-Id: I24a17ec019409930883da8040fe2fb05b0fea0c5
Signed-off-by: Bernhard Rosenkraenzer <Bernhard.Rosenkranzer@linaro.org>