android: egl: add libsync_cflags to the build

android: egl: add libsync_cflags to the build

... via local_shared_libraries. Otherwise the sync/sync.h header won't
be found.

Note: 10.5 and earlier will need similar change in st/egl.

v2: Append the library to the local_shared_libraries list. (Chih-Wei)

Cc: "10.4 10.5" <mesa-stable@lists.freedesktop.org>
Signed-off-by: Emil Velikov <emil.l.velikov@gmail.com>
Reviewed-by: Chih-Wei Huang <cwhuang@linux.org.tw>
(cherry picked from commit 2d06791f6f9e8ab37109be52e63d247bbbcb42d4)