BaseTools: remove -DNO_MSABI_VA_FUNCS option in CLANGPDB tool chain

BaseTools: remove -DNO_MSABI_VA_FUNCS option in CLANGPDB tool chain

REF: https://bugzilla.tianocore.org/show_bug.cgi?id=2524

remove -DNO_MSABI_VA_FUNCS option in CLANGPDB tool chain After CLANGPDB is
switched to GNU mode, to use MS ABI version of GCC built-in macros for
variable argument lists as same as CLANG38 tool chain.

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: Liming Gao <liming.gao@intel.com>