BaseTools: accept 'amd64' as an alias for 'x86_64'

On FreeBSD uname -a reports 'amd64' for the 64-bit x86 architecture.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Ed Maste <emaste@freebsd.org>
Reviewed-by: Laszlo Ersek <lersek@redhat.com>
Reviewed-by: Jordan Justen <jordan.l.justen@intel.com>
Reviewed-by: Liming Gao <liming.gao@intel.com>

git-svn-id: https://svn.code.sf.net/p/edk2-buildtools/code/trunk/BaseTools@2661 c2973edb-eda0-4c78-bc6a-9341b269661f
BaseTools: Use $(MAKE) variable to invoke a sub-make

On FreeBSD GNU make is typically installed as gmake.  Support this by
using $(MAKE), the standard way to invoke a sub-make.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Ed Maste <emaste@freebsd.org>
Reviewed-by: Jordan Justen <jordan.l.justen@intel.com>

git-svn-id: https://svn.code.sf.net/p/edk2-buildtools/code/trunk/BaseTools@2662 c2973edb-eda0-4c78-bc6a-9341b269661f