Implement -frecord-command-line for XCOFF

This patch extends support of the option `-frecord-command-line` to XCOFF. XCOFF doesn’t have custom sections like ELF, so the command line data is emitted to a .info section instead. A C_INFO symbol is generated with the .info section to preserve the command line data past the link step. Multiple command lines are separated by newlines and null bytes. The command line data can be retrieved on AIX with command `what file_name`.

Reviewed By: scott.linder

Differential Revision: https://reviews.llvm.org/D153600