Keep _FORTIFY_SOURCE=2 for libvulkan when enabling _FORTIFY_SOURCE=3 globally

malloc_usable_size() is not allowed when _FORTIFY_SOURCE=3, so we keep
it 2 as a workaround.

Bug: b/291762537
Test: mm and presubmit
Change-Id: I2eb79bb9673aacfd36b0835edbf821059319189f
1 file changed