Merge "Revert "Use -O2 temporarily because of compiler crash"" am: 33872108b7 am: 6febc069ce am: 4bf14f37af

Original change: https://android-review.googlesource.com/c/platform/external/pdfium/+/1908657

Change-Id: I47b741dfc14c03aaa5f6f19a19191b3a4e05c2b7