This allows the linker to move the variables from the .data section to
the .rodata section.

Bug: libyuv:254
Test: out/Release/libyuv_unittest --gtest_filter=* --libyuv_width=1280 --libyuv_height=720 --libyuv_repeat=999 --libyuv_flags=-1 --libyuv_cpu_info=-1

Change-Id: I6998570f1af4337d7b80313d9e18e36aa20d6ec0
Reviewed-on: https://chromium-review.googlesource.com/777033
Commit-Queue: Frank Barchard <fbarchard@chromium.org>
Reviewed-by: Frank Barchard <fbarchard@chromium.org>