Ref: https://bugzilla.tianocore.org/show_bug.cgi?id=2842 To use LLVM to build BaseTools, first set the CLANG_BIN environment value, and add "CXX=llvm" to choose LLVM compiler set when using make command. Cc: Bob Feng <bob.c.feng@intel.com> Cc: Liming Gao <liming.gao@intel.com> Signed-off-by: Zhiguang Liu <zhiguang.liu@intel.com> Reviewed-by: Bob Feng <bob.c.feng@intel.com> Reviewed-by: Yuwei Chen<yuwei.chen@intel.com>