Android: Add a CMAKE_BUILD_TYPE default

Android NDK builds are always `debug` or `release`.  We may populate
flags for these configurations that are needed to produce compatible
binaries.  Ensure they are used by default.

Modules/Platform/Android-Initialize.cmake

@@ -47,3 +47,5 @@ else()
     "Android: No CMAKE_SYSROOT was selected."
     )
 endif()
+
+set(CMAKE_BUILD_TYPE_INIT Debug)