Re-enable ThinLTO for libandroid_runtime

This partially reverts commit cd1e70b874f811e74efb20f650cf427cc685c2b6.

Breakages are fixed in the current stable Clang.

Test: presubmit
Bug: 169004486
Change-Id: I2c69f7fc195aaa1f45249ef735860f0c50fe61fa
1 file changed