1. Following the setup of gcc in build/core/combo/,
we added the [HOST|TARGET]_<arch>.mk clang config files,
and load only the configs needed by the current product.
2. Added support for the 2nd arch.
Change-Id: I2a383418a9688a050b39492f8e489d40eeeb5f2d
The rules for the 2nd arch are set up in the second inclusion
of shared_library_internal.mk.
Intermediate fils of libfoo of the 2nd arch will be built into
$(PRODUCT_OUT)/obj_$(TARGET_2ND_ARCH)/SHARED_LIBRARIES/libfoo_intermediates/
and the built libfoo.so will be in
$(PRODUCT_OUT)/obj_$(TARGET_2ND_ARCH)/lib.
Bug: 11654773
Change-Id: I58bbe5a05a65f63bce6279131552f3792000716e