install: remove /mnt/pmbootstrap at the end

Don't include the /mnt/pmbootstrap directories in the images created
with "pmbootstrap install".

Reviewed-by: Pablo Correa Gómez <ablocorrea@hotmail.com>
Reviewed-by: Luca Weiss <luca@z3ntu.xyz>
Link: https://lists.sr.ht/~postmarketos/pmbootstrap-devel/%3C20230806184729.4891-3-ollieparanoid@postmarketos.org%3E

test/test_chroot_mount.py

@@ -0,0 +1,40 @@
+# Copyright 2023 Oliver Smith
+# SPDX-License-Identifier: GPL-3.0-or-later
+""" Test pmb/chroot/mount.py """
+import os
+import pytest
+import sys
+
+import pmb_test  # noqa
+import pmb.chroot
+
+
+@pytest.fixture
+def args(tmpdir, request):
+    import pmb.parse
+    sys.argv = ["pmbootstrap", "init"]
+    args = pmb.parse.arguments()
+    args.log = args.work + "/log_testsuite.txt"
+    pmb.helpers.logging.init(args)
+    request.addfinalizer(pmb.helpers.logging.logfd.close)
+    return args
+
+
+def test_chroot_mount(args):
+    suffix = "native"
+    mnt_dir = f"{args.work}/chroot_native/mnt/pmbootstrap"
+
+    # Run something in the chroot to have the dirs created
+    pmb.chroot.root(args, ["true"])
+    assert os.path.exists(mnt_dir)
+    assert os.path.exists(f"{mnt_dir}/packages")
+
+    # Umount everything, like in pmb.install.install_system_image
+    pmb.helpers.mount.umount_all(args, f"{args.work}/chroot_{suffix}")
+
+    # Remove all /mnt/pmbootstrap dirs
+    pmb.chroot.remove_mnt_pmbootstrap(args, suffix)
+    assert not os.path.exists(mnt_dir)
+
+    # Run again: it should not crash
+    pmb.chroot.remove_mnt_pmbootstrap(args, suffix)