The target gtk+3 does a native build in its "native" directory, we need
unset the target FLAGS for native build, otherwise, there might be build
failures.
(From OE-Core rev: 3f3e249b98182fa50358ade9278e3e26454275b8)
Signed-off-by: Robert Yang <liezhi.yang@windriver.com>
Signed-off-by: Saul Wold <sgw@linux.intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>