[Debug-Info][CodeView] Fix GUID string generation for MSVC generated objects.

This patch is to address https://bugs.llvm.org/show_bug.cgi?id=50459.
  YAML:455:28: error: GUID strings are 38 characters long

The valid format for a GUID is {XXXXXXXX-XXXX-XXXX-XXXX-XXXXXXXXXXXX}
where X is a hex digit (0,1,2,3,4,5,6,7,8,9,A,B,C,D,E,F).
The length of the individual components must be: 8, 4, 4, 4, 12.

For some cases, the converted string generated by obj2yaml, does not
comply with those lengths. yaml2obj checks that the GUID string must
be 38 characters including the dashes and braces.

Reviewed By: amccarth

Differential Revision: https://reviews.llvm.org/D103089