Fix the Windows adb build.

It looks like we can't use clang on Windows yet because libc++ isn't ready.
So move back to GCC for the Windows host clang. Work around the mingw
printf format string problems that made us want to switch to clang in the
first place, and #include "sysdeps.h" in adb_utils.cpp to work around the
absence of lstat(2) on Windows.

Change-Id: Icd0797a8c0c2d1d326bdd704ba6bcafcbaeb742f