Replace API level codename with number

This CL fixes a bug when Soong pass `-target` with a non-digit suffix in Clang. As mentioned in b/236753843, Clang's version parsing expects to see an integer in the target string so it ignores the
S suffix.

Test: m gwp_asan_crash_handler && make sure -target is aarch64-linux-androidS instead of aarch64-linux-android31
Test: go test -run ^TestNonDigitMinSdkVersionInClangTriple$ android/soong/cc
Bug: 236753843
Change-Id: I258ecc52083dbf3471d23cf310e0ad54440f1908