BaseTools/build.py: Exit with 1 when AutoGen error occurred

BaseTools/build.py: Exit with 1 when AutoGen error occurred

AutoGen manager/workers halt the progress when an error occurs but
doesn't propagate the error code to main and allows main exit with 0
and gets the build system unable to catch the occurrence of an error.
This change informs main with an error when a progress is halted and
helps main exit with 1.

Signed-off-by: Irene Park <ipark@nvidia.com>
Reviewed-by: Bob Feng<bob.c.feng@intel.com>