[android] Add a test for Android conditional compilation (AArch64)

There are similar tests for other architectures/OS pairs, but
android-aarch64 was missing. This should ensure that the conditional
compilation for Android works correctly in this case.

Author: drodriguez

test/Parse/ConditionalCompilation/aarch64AndroidTarget.swift

@@ -0,0 +1,14 @@
+// RUN: %swift -typecheck %s -verify -target aarch64-none-linux-android -disable-objc-interop -parse-stdlib
+// RUN: %swift-ide-test -test-input-complete -source-filename=%s -target aarch64-none-linux-android
+
+#if os(Linux)
+// This block should not parse.
+// os(Android) does not imply os(Linux).
+let i: Int = "Hello"
+#endif
+
+#if arch(arm64) && os(Android) && _runtime(_Native) && _endian(little)
+class C {}
+var x = C()
+#endif
+var y = x