Revert "Disable `perf` support in the profiler when running on Android (for now)."

This reverts commit 8e35b7d01e14371851a806dad6196b36d9163c91.

The fallback implementation (as used on other platforms) appears to hang
the runtime. Having a maybe-working `perf`-backed sample profiler is better
than a not-working sample profiler.
Remove the architecture conditions for using `perf` in the log profiler.

We now use generic atomics which work on all platforms, so there's
no reason to keep this constraint here. This allows the `perf`-backed
profiler to be used on mips, ppc, s390x, etc.