BaseTools:Double carriage return inserted from Trim.py on Python3

BaseTools:Double carriage return inserted from Trim.py on Python3

https://bugzilla.tianocore.org/show_bug.cgi?id=1379

Line 208 of BaseTools/Source/Python/Trim/Trim.py uses
'NewLines.append(os.linesep)' to insert a new line into
the list that will be written to the output file.
This causes the '\r\n' inserted with os.linesep to be
written as '\r\r\n', causing some assemblers to error.

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>
Tested-by: Laszlo Ersek <lersek@redhat.com>
Tested-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Reviewed-by: Liming Gao <liming.gao@intel.com>
Reviewed-by: Bob Feng <bob.c.feng@intel.com>