BaseTools: Barf on unknown HOST_ARCH in C Makefile

BaseTools: Barf on unknown HOST_ARCH in C Makefile

I was getting `HOST_ARCH` set using the linux arch name ("x86_64"), which
is different from the MS one ("X64").

It is not clear anyway we can proceed without valid build variables
(`ARCH_INCLUDE`, `BIN_PATH`, `LIB_PATH`, `SYS_BIN_PATH`, and
`SYS_LIB_PATH`).

Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Chema Gonzalez <chemag@gmail.com>
Reviewed-by: Liming Gao <liming.gao@intel.com>