Unify skip and only logic for build scripts

And switch to a single file that can include mcu, family or board.

tools/build_utils.py

@@ -0,0 +1,61 @@
+import pathlib
+
+def skip_example(example, board):
+    ex_dir = pathlib.Path('examples/') / example
+    bsp = pathlib.Path("hw/bsp")
+
+    board_dir = list(bsp.glob("*/boards/" + board))
+    if not board_dir:
+        # Skip unknown boards
+        return True
+
+    board_dir = list(board_dir)[0]
+    
+    family_dir = board_dir.parent.parent
+    family = family_dir.name
+
+    # family CMake
+    family_mk = family_dir / "family.cmake"
+
+    # family.mk
+    if not family_mk.exists():
+        family_mk = family_dir / "family.mk"
+
+    mk_contents = family_mk.read_text()
+
+    # Find the mcu
+    if "CFG_TUSB_MCU=OPT_MCU_" not in mk_contents:
+        board_mk = board_dir / "board.cmake"
+        if not board_mk.exists():
+            board_mk = board_dir / "board.mk"
+
+        mk_contents = board_mk.read_text()
+
+    for token in mk_contents.split():
+        if "CFG_TUSB_MCU=OPT_MCU_" in token:
+            # Strip " because cmake files has them.
+            token = token.strip("\"")
+            _, opt_mcu = token.split("=")
+            mcu = opt_mcu[len("OPT_MCU_"):]
+
+    # Skip all OPT_MCU_NONE these are WIP port
+    if mcu == "NONE":
+        return True
+
+    skip_file = ex_dir / "skip.txt"
+    only_file = ex_dir / "only.txt"
+
+    if skip_file.exists() and only_file.exists():
+        raise RuntimeError("Only have a skip or only file. Not both.")
+    elif skip_file.exists():
+        skips = skip_file.read_text().split()
+        return ("mcu:" + mcu in skips or
+                "board:" + board in skips or
+                "family:" + family in skips)
+    elif only_file.exists():
+        onlys = only_file.read_text().split()
+        return not ("mcu:" + mcu in onlys or
+                    "board:" + board in onlys or
+                    "family:" + family in onlys)
+
+    return False