Fix cygwin test failure due to shortpath usage

Two tests are failing on Cygwin because the argument is passed as
a long-path and the Path is ending up as a short-path:

AllPlatformTests.test_run_target_files_path

  Traceback (most recent call last):
    File "/cygdrive/d/a/meson/meson/test cases/common/51 run target/check-env.py", line 22, in <module>
      assert build_root == env_build_root
  AssertionError

SubprojectsCommandTests.test_purge

  >       self.assertEqual(deleting(out), sorted([
              str(self.subprojects_dir / 'redirect.wrap'),
              str(self.subprojects_dir / 'sub_file'),
              str(self.subprojects_dir / 'sub_git'),
          ]))
  E       AssertionError: Lists differ: ['/cygdrive/c/Users/runneradmin/AppData/Local/Temp/tmpeaa2a49[205 chars]git'] != ['/cygdrive/c/Users/RUNNER~1/AppData/Local/Temp/tmpeaa2a49z/s[196 chars]git']

  [...]

  ['/cygdrive/c/Users/runneradmin/AppData/Local/Temp/tmpeaa2a49z/src/subprojects/redirect.wrap',
                      ^^^^^^^^^^^
  ['/cygdrive/c/Users/RUNNER~1/AppData/Local/Temp/tmpeaa2a49z/src/subprojects/redirect.wrap',
                      ^^^^^^^^

The fix is to not use the tempdir for all tests, but only for tests
that check the mode.

1 files changed, 15 insertions, 8 deletions

diff --git a/unittests/baseplatformtests.py b/unittests/baseplatformtests.py
index 9371395..bd2f902 100644
--- a/unittests/baseplatformtests.py
+++ b/unittests/baseplatformtests.py
@@ -100,14 +100,21 @@ class BasePlatformTests(TestCase):
         self.builddirs.append(self.builddir)
 
     def new_builddir(self):
-        if not is_cygwin():
-            # Keep builddirs inside the source tree so that virus scanners
-            # don't complain
-            newdir = tempfile.mkdtemp(dir=os.getcwd())
-        else:
-            # But not on Cygwin because that breaks the umask tests. See:
-            # https://github.com/mesonbuild/meson/pull/5546#issuecomment-509666523
-            newdir = tempfile.mkdtemp()
+        # Keep builddirs inside the source tree so that virus scanners
+        # don't complain
+        newdir = tempfile.mkdtemp(dir=os.getcwd())
+        # In case the directory is inside a symlinked directory, find the real
+        # path otherwise we might not find the srcdir from inside the builddir.
+        newdir = os.path.realpath(newdir)
+        self.change_builddir(newdir)
+
+    def new_builddir_in_tempdir(self):
+        # Can't keep the builddir inside the source tree for the umask tests:
+        # https://github.com/mesonbuild/meson/pull/5546#issuecomment-509666523
+        # And we can't do this for all tests because it causes the path to be
+        # a short-path which breaks other tests:
+        # https://github.com/mesonbuild/meson/pull/9497
+        newdir = tempfile.mkdtemp()
         # In case the directory is inside a symlinked directory, find the real
         # path otherwise we might not find the srcdir from inside the builddir.
         newdir = os.path.realpath(newdir)