Default host module to 64-bit except for SDK builds.

Set "HOST_PREFER_32_BIT := true" only if "sdk" or "win_sdk" is among the
make command line goals, or it's a MinGW windows build, which only builds
host SDK tools.

Bug: 13751317
Change-Id: I8ec1a97a5d1af065a153b16523c2ee3434d0dd71