/dev/shm is currently mounted with noexec

`/dev/shm` is currently mounted with noexec, there one can not for example run `configure` scripts inside `/dev/shm` when building code off-tree.

```
fedora-toolbox-41 [pbrezina /dev/shm/authselect]$ ~/workspace/authselect/configure --enable-silent-rules --prefix=/dev/shm/authselect-install
checking for gcc... gcc
checking whether the C compiler works... yes
checking for C compiler default output file name... a.out
checking for suffix of executables...
checking whether we are cross compiling... configure: error: in '/dev/shm/authselect':
configure: error: cannot run C compiled programs.
If you meant to cross compile, use '--host'.
See 'config.log' for more details
```

```
$ mount | grep shm
tmpfs on /dev/shm type tmpfs (rw,nosuid,nodev,seclabel,inode64)
tmpfs on /dev/shm type tmpfs (rw,nosuid,nodev,noexec,seclabel,inode64)
tmpfs on /run/host/dev/shm type tmpfs (rw,nosuid,nodev,seclabel,inode64)
```

The workaround can be to use `/run/host/dev/shm`, but I think toolbox should allow exec bits on `/dev/shm` as well, given its development purpose.