handle more corner cases where locking the build directory fails

This can raise any OSError, but we only caught two of them that indicate
a particular failure case. Also catch the generic error form with a more
generic message.

This produces better error messages in cases where e.g. exclusive lock
is not supported.

mesonbuild/utils/posix.py

@@ -34,6 +34,9 @@ class BuildDirLock(BuildDirLockBase):
         except (BlockingIOError, PermissionError):
             self.lockfile.close()
             raise MesonException('Some other Meson process is already using this build directory. Exiting.')
+        except OSError as e:
+            self.lockfile.close()
+            raise MesonException(f'Failed to lock the build directory: {e.strerror}')
 
     def __exit__(self, *args: T.Any) -> None:
         fcntl.flock(self.lockfile, fcntl.LOCK_UN)