Support compiling python3 against musl

Use bool instead of _Bool in android/launcher_main.cpp, _Bool isn't
defined in C++, and musl doesn't manually define it like glibc does.

Adjust the configuration header for musl.

Bug: 190084016
Test: m out/soong/host/linux-x86/bin/py3-run with musl
Change-Id: I6c7e6f42d65bffa07da3811dbeda7822b2804e63