Mark android_cross_compile.test unsupported for iOS, tvOS, and watchOS

Author: shahmishal

validation-test/BuildSystem/android_cross_compile.test

@@ -1,5 +1,8 @@
 # REQUIRES: standalone_build
 # UNSUPPORTED: OS=macosx
+# UNSUPPORTED: OS=ios
+# UNSUPPORTED: OS=tvos
+# UNSUPPORTED: OS=watchos
 
 # RUN: %empty-directory(%t)
 # RUN: SWIFT_BUILD_ROOT=%t %swift_src_root/utils/build-script --dry-run --cmake %cmake --libdispatch --cross-compile-hosts=android-aarch64 --skip-local-build --android --android-ndk %t/ndk/ --android-arch aarch64 --android-icu-uc %t/lib/libicuuc.so --android-icu-uc-include %t/include/ --android-icu-i18n %t/lib/libicui18n.so --android-icu-i18n-include %t/include/ --android-icu-data %t/lib/libicudata.so 2>&1 | %FileCheck %s