os/exec: Plan 9 build has been broken by a Windows security fix (also breaks 1.19.3 and 1.18.8) [1.18 backport] #56550
Description
@mdempsky requested issue #56544 to be considered for backport to the next 1.18 minor release.
@gopherbot Please backport to 1.18 and 1.19. The Windows security fix inadvertently broke Plan 9.