[nrf fromtree] scripts: list_boards: Reintroduce Board.dir as @Property

In the `Board` class, the `dir` member was renamed to `directories`,
both to indicate that it is now a list (in HWMv2 with board extensions)
and to reflect the addition of the `BOARD_DIRECTORIES` CMake variable.
Considering that the build system also keeps the `BOARD_DIR` variable,
and for the sake of backwards compatibility and brevity, it should be
useful to retain `Board.dir` in Python as well, symmetrically.

Signed-off-by: Grzegorz Swiderski <[email protected]>
(cherry picked from commit a1f3f88)

Author: 57300

scripts/list_boards.py

@@ -104,6 +104,13 @@ class Board:
     socs: List[Soc] = field(default_factory=list, compare=False)
     variants: List[str] = field(default_factory=list, compare=False)
 
+    @property
+    def dir(self):
+        # Get the main board directory.
+        if isinstance(self.directories, Path):
+            return self.directories
+        return self.directories[0]
+
     def from_qualifier(self, qualifiers):
         qualifiers_list = qualifiers.split('/')