Workaround using new Clang with an old NDK.
Workaround using new Clang with an old NDK.

We're using an old NDK and a new Clang. New Clangs default to
`-stdlib=libc++` for Android, but those libraries cannot be found by
default with an old NDK. Use an explicit `-stdlib=libstdc++` in the
cxx_mode_flags.

git-svn-id: c199f293c43da69278bea8e88f92242bf3aa95f7@346051 91177308-0d34-0410-b5e6-96231b3b80d8

llvm-mirror/compiler-rt,llvm-mirror/compiler-rt,llvm-mirror/compiler-rt,llvm-mirror/compiler-rt,llvm-mirror/compiler-rt