syscall: installing Go in chroot chronically fails on TestCloneNEWUSERAndRemapRootDisableSetgroups if /proc/sys/kernel/unprivilged_userns_clone is not 1

[Ulmo]

I'm installing the latest go in a chroot, and I'm getting a repeat of the error in #11261, but this time, the patch mentioned in #11261 (http://golang.org/cl/11269) doesn't stop the bug. I manually set that kernel variable (/proc/sys/kernel/unprivileged_userns_clone) to 0 rather than 1, and then the test succeeded, so that is a workaround, but the error still happened in the first place.

This workaround allowed Go to be installed successfully.

I am not going to repeat the data in #11261 since that already explained the background.

[odeke-em]

Thank you for this report @Ulmo and welcome to the Go project!

I've updated the issue title accordingly and thanks for pointing out the remedy of your workaround.
Kindly pinging perhaps some interested parties @LK4D4 @ianlancetaylor @ALTree.