remove GCC build warning

Fix gcc: warning:
 -x c after last input file has no effect

These kind of flag can only affect the source code after them.
For the build command in build_rule.template, we have no other source code or object after these two flag.
It seems we don't need them here.

Cc: Bob Feng <bob.c.feng@intel.com>
Cc: Liming Gao <gaoliming@byosoft.com.cn>
Cc: Yuwei Chen <yuwei.chen@intel.com>
Signed-off-by: JessyX Wu <jessyx.wu@intel.com>
Reviewed-by: Liming Gao <gaoliming@byosoft.com.cn>
Reviewed-by: Bob Feng <bob.c.feng@intel.com>