[safestack] Driver link test for safestack on android.
[safestack] Driver link test for safestack on android.

Safestack runtime should never be linked on Android targets because
it is implemented directly in libc. This is already the case, but
mostly by chance (collectSanitizerRuntimes would only link shared
sanitizer runtimes, and safestack has only a static one). Protect
this behavior with a test.

git-svn-id: ffe668792ed300d6c2daa1f6eba2e0aa28d7ec6c@250128 91177308-0d34-0410-b5e6-96231b3b80d8

llvm-mirror/clang,llvm-mirror/clang,apple/swift-clang,apple/swift-clang,llvm-mirror/clang,llvm-mirror/clang,llvm-mirror/clang,llvm-mirror/clang,apple/swift-clang,apple/swift-clang,apple/swift-clang,llvm-mirror/clang,llvm-mirror/clang,apple/swift-clang,apple/swift-clang,llvm-mirror/clang,llvm-mirror/clang,apple/swift-clang,apple/swift-clang,apple/swift-clang