Regenerate views when specs already installed (#28113)
Regenerate views when specs already installed (#28113)

With this commit:
```
$ spack env activate --temp
$ spack install zlib
==> All of the packages are already installed
==> Updating view at /tmp/spack-faiirgmt/.spack-env/view
$ spack install zlib
==> All of the packages are already installed
```

Before this PR:
```
$ spack env activate --temp
$ spack install zlib
==> All of the packages are already installed
$ spack install zlib
==> All of the packages are already installed
```

No view was generated

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