The previously used syntax, -Wl,-pdb,<file>, was the originally supported one in lld (since 2018). Later (in 2019) the second syntax was added, allowing both -Wl,-pdb=<file> and -Wl,-pdb,<file>. (This other parameter syntax allows easier distinguishing an empty argument, for letting the linker implicitly pick the file name.)
Move over to using the more modern syntax - reducing the usage of the old form of the option. This potentially allows deprecating the original syntax and maybe allows using --pdb as a boolean flag for implying an automatically named PDB file (which currently requires using the awkward syntax "--pdb=").
Also prefer the long two dashes form, i.e. --pdb instead of -pdb; the single dash form is only allowed by getopt when there are no conflicts with single-letter options, while the form with two dashes is unambiguous.