BaseTools:Trim will trig exception when input asl UTF8 format file

BaseTools:Trim will trig exception when input asl UTF8 format file

BZ:https://bugzilla.tianocore.org/show_bug.cgi?id=1641

The command trim --asl-file -o test.i UTF8.asl will trig the exception.
Trim tool should report error message for unsupported UTF8 file instead
of the exception.

Cc: Bob Feng <bob.c.feng@intel.com>
Cc: Liming Gao <liming.gao@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Zhiju.Fan <zhijux.fan@intel.com>
Reviewed-by: Liming Gao <liming.gao@intel.com>