Fix SDL2 .pc files for qemu-android build.

This patch corresponds to the changes in build-qemu-android-deps.sh
described here:

  https://android-review.googlesource.com/#/c/153350/

There is no point to update the rest of the binary files, so the
change has been limited to the sdl2.pc files after re-running the
script.

Change-Id: Ia3e3461aebeb878cb839245bd5a8f12e91e3ad4c