BaseTools/Source/C/Makefiles: Fix NmakeSubdirs.bat always return 0

BaseTools/Source/C/Makefiles: Fix NmakeSubdirs.bat always return 0

In batch script file NmakeSubdirs.bat, the value changes made to the
variable 'TOOL_ERROR' within the 'setlocal...endlocal' block will not be
reflected in the return value of the script. A value of 0 will always be
returned. Thus, the script will not reflect the result of the 'nmake'
command correctly when building BaseTool source codes.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Hao Wu <hao.a.wu@intel.com>
Reviewed-by: Yonghong Zhu <yonghong.zhu@intel.com>