BaseTools: Add RISCV64 binding

- Add RISCV64 ProcessorBind.h

- Add RISCV64 to Makefiles

Signed-off-by: Nikita Ermakov <sh1r4s3@mail.si-head.nl>
Ack-by: Liming Gao <gaoliming@byosoft.com.cn>
Acked-by: Abner Chang <abner.chang@hpe.com>

BaseTools/Source/C/GNUmakefile

@@ -26,6 +26,9 @@ ifndef HOST_ARCH
   else ifneq (,$(findstring arm,$(uname_m)))
     HOST_ARCH=ARM
   endif
+  ifneq (,$(findstring riscv64,$(uname_m)))
+    HOST_ARCH=RISCV64
+  endif
   ifndef HOST_ARCH
     $(info Could not detected HOST_ARCH from uname results)
     $(error HOST_ARCH is not defined!)