tests hang when umask is 027

[Tom Payne]

Describe the bug

Running go test ./... hangs when umask is 027, as identified by @kjkent in #3847 (comment).

To reproduce

$ umask 027
$ go test ./...

Expected behavior

chezmoi's tests complete successfully in a timely manner.

Output of command with the --verbose flag

n/a

Output of chezmoi doctor

$ chezmoi doctor
RESULT   CHECK                       MESSAGE
ok       version                     v2.49.1, commit Homebrew, built at 2024-06-23T11:05:46Z, built by Homebrew
ok       latest-version              v2.49.1
ok       os-arch                     darwin/arm64
ok       uname                       Darwin Toms-Laptop 23.5.0 Darwin Kernel Version 23.5.0: Wed May  1 20:14:59 PDT 2024; root:xnu-10063.121.3~5/RELEASE_ARM64_T8122 arm64
ok       go-version                  go1.22.4 (gc)
ok       executable                  /opt/homebrew/bin/chezmoi
ok       upgrade-method              brew-upgrade
ok       config-file                 ~/.config/chezmoi/chezmoi.toml, last modified 2024-04-28T14:47:49+02:00
ok       source-dir                  ~/.local/share/chezmoi is a git working tree (clean)
ok       suspicious-entries          no suspicious entries
ok       working-tree                ~/.local/share/chezmoi is a git working tree (clean)
ok       dest-dir                    ~ is a directory
ok       umask                       022
ok       cd-command                  found /bin/zsh
ok       cd-args                     /bin/zsh
info     diff-command                not set
ok       edit-command                found /opt/homebrew/bin/nvim
ok       edit-args                   /opt/homebrew/bin/nvim
ok       git-command                 found /opt/homebrew/bin/git, version 2.45.2
ok       merge-command               found /usr/bin/vimdiff
ok       shell-command               found /bin/zsh
ok       shell-args                  /bin/zsh
ok       age-command                 found /opt/homebrew/bin/age, version 1.2.0
ok       gpg-command                 found /opt/homebrew/bin/gpg, version 2.4.5
info     pinentry-command            not set
ok       1password-command           found /opt/homebrew/bin/op, version 2.29.0
info     bitwarden-command           bw not found in $PATH
info     bitwarden-secrets-command   bws not found in $PATH
info     dashlane-command            dcli not found in $PATH
info     doppler-command             doppler not found in $PATH
info     gopass-command              gopass not found in $PATH
info     keepassxc-command           keepassxc-cli not found in $PATH
info     keepassxc-db                not set
info     keeper-command              keeper not found in $PATH
info     lastpass-command            lpass not found in $PATH
info     pass-command                pass not found in $PATH
info     passhole-command            ph not found in $PATH
info     rbw-command                 rbw not found in $PATH
info     vault-command               vault not found in $PATH
info     vlt-command                 vlt not found in $PATH
info     secret-command              not set```

</details>

## Additional context

n/a