cmd/link: support more load commands on Mach-O [1.16 backport] #49923
Description
On the 1.16 release branch, the macOS 12 builder has been failing since it was brought up, basically.
The failures look like https://build.golang.org/log/158c3565da1dabd522292bee52369d329419a452 with a bunch of misc/cgo/testcshared tests failing.