BaseTools: BaseTools changes for RISC-V platform.

BaseTools: BaseTools changes for RISC-V platform.

Python code changes for building EDK2 RISC-V platform.

Signed-off-by: Abner Chang <abner.chang@hpe.com>
Co-authored-by: Gilbert Chen <gilbert.chen@hpe.com>
Co-authored-by: Daniel Helmut Schaefer <daniel.schaefer@hpe.com>
Reviewed-by: Leif Lindholm <leif.lindholm@linaro.org>
Reviewed-by: Bob Feng <bob.c.feng@intel.com>
Cc: Bob Feng <bob.c.feng@intel.com>
Cc: Liming Gao <liming.gao@intel.com>
Cc: Leif Lindholm <leif.lindholm@linaro.org>
Cc: Gilbert Chen <gilbert.chen@hpe.com>