ANDROID: Compile kselftest_timers_posix_timers code

This partially reverts commit f3a29e7e.

Reason of revert: pthread_cancel symbol is added, so test can compile.
However the tests still fail for two reasons:
1. pthread_cancel needs to be substituted with a functional equivalent
   in Android.
2. they depend on future patches: "(the tests) fail for now until the
   signal and posix timer code is updated."

Bug: 369330443
Bug: 369693249
Change-Id: Icbb34b4726c2bb9d782cad27478a0c63e3785f96
Signed-off-by: HONG Yifan <elsk@google.com>
Signed-off-by: Edward Liaw <edliaw@google.com>