Add support for cross compiling Windows tools on Darwin.

Change-Id: Iba04ca9cc02f4b7059fcfb8362373a72e0365be8
Fix up Windows cross compile detection and error handling on Darwin.

Change-Id: Iaa0e3aa64340e31c357a60bc774d9a4ec8174f62
Merge remote-tracking branch 'origin/cm-10.1' into cm-10.1-linaro