Spack can now be configured to assign permissions to the files installed by a package.
In the `packages.yaml` file under `permissions`, the attributes `read`, `write`, and `group` control the package permissions. These attributes can be set per-package, or for all packages under `all`. If permissions are set under `all` and for a specific package, the package-specific settings take precedence. The `read` and `write` attributes take one of `user`, `group`, and `world`.
packages:
all:
permissions:
write: group
group: spack
my_app:
permissions:
read: group
group: my_team
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