chromium: fix aarch64 build

The skia patch no longer applies, and is no longer necessary.

The current version of chromium doesn't build with gcc. This has been
fixed upstream[1] and could be backported, but switching aarch64 to
clang/llvm and making the build the same on all platforms is simpler.

[1] https://chromium.googlesource.com/chromium/src/+/9662ec844017690d5fd56bf0f05ef6a540dd29c1