Support to build executables for TARGET_2ND_ARCH

By default, an executable is built for TARGET_ARCH.
To build it for TARGET_2ND_ARCH in a 64bit product, use:
LOCAL_32BIT_ONLY := true
To skip a module for TARGET_2ND_ARCH, use:
LOCAL_NO_2ND_ARCH := true

Bug: 11654773
Change-Id: Ieb293d25b21024bfe1b554044df338e064ac7b46