OvmfPkg/build.sh: Add support for GCC49 toolchain

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Jordan Justen <jordan.l.justen@intel.com>
Reviewed-by: Laszlo Ersek <lersek@redhat.com>

git-svn-id: svn://svn.code.sf.net/p/edk2/code/trunk/edk2/OvmfPkg@15698 6f19259b-4bc3-4df7-8a09-765794883524
OvmfPkg/build.sh: Support IA32+X64 build

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Jordan Justen <jordan.l.justen@intel.com>
Reviewed-by: Laszlo Ersek <lersek@redhat.com>

git-svn-id: svn://svn.code.sf.net/p/edk2/code/trunk/edk2/OvmfPkg@15703 6f19259b-4bc3-4df7-8a09-765794883524