os/exec: TestFindExecutableVsNoexec failing on linux-ppc64-sid-buildlet since go.dev/cl/414824

[mknyszek]

Example failure: https://build.golang.org/log/94be4739468ce56e170e8b9ca55b5e2fb95e4d1f

CC @kolyshkin @ianlancetaylor

[gopherbot]

Change https://go.dev/cl/429217 mentions this issue: Revert "os/exec: LookPath: use eaccess for exec check on linux"

[mknyszek]

Waiting on https://go.dev/cl/429175.