Android: Add placeholders for platform-specific compiler selection

Add infrastructure modules to be loaded for determining a compiler
selection when targeting Android platforms.

Modules/Platform/Android-Determine-C.cmake

+include(Platform/Android/Determine-Compiler)
+__android_determine_compiler(C)

Modules/Platform/Android-Determine-CXX.cmake

+include(Platform/Android/Determine-Compiler)
+__android_determine_compiler(CXX)

Modules/Platform/Android/Determine-Compiler.cmake

+#=============================================================================
+# Copyright 2015-2016 Kitware, Inc.
+#
+# Distributed under the OSI-approved BSD License (the "License");
+# see accompanying file Copyright.txt for details.
+#
+# This software is distributed WITHOUT ANY WARRANTY; without even the
+# implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+# See the License for more information.
+#=============================================================================
+# (To distribute this file outside of CMake, substitute the full
+#  License text for the above reference.)
+
+# This module is shared by multiple languages; use include blocker.
+if(__ANDROID_DETERMINE_COMPILER)
+  return()
+endif()
+set(__ANDROID_DETERMINE_COMPILER 1)
+
+macro(__android_determine_compiler lang)
+endmacro()