fbt/ufbt: Ensure POSIX paths are passed to GDB on all platforms (#3360)

* fbt/ufbt: Ensure POSIX paths are passed to GDB on all platforms
  GDB heavily dislikes forward slashes from Windows paths and strips
  them internally instead of normalizing them. Account for this by
  passing POSIX paths explicitly.
* fbt: different approach for posix path handling
* fbt, ufbt: further fixes for path handling
* fbt: explicit path stringification
* linter fixes

Co-authored-by: hedger <hedger@users.noreply.github.com>
Co-authored-by: hedger <hedger@nanode.su>
Co-authored-by: あく <alleteam@gmail.com>

scripts/fbt/util.py

@@ -3,6 +3,7 @@ import re
 import subprocess
 import sys
 import webbrowser
+from pathlib import Path, PurePosixPath
 
 import SCons
 from SCons.Errors import StopError
@@ -82,6 +83,27 @@ def resolve_real_dir_node(node):
     raise StopError(f"Can't find absolute path for {node.name} ({node})")
 
 
+class PosixPathWrapper:
+    def __init__(self, pathobj):
+        self.pathobj = pathobj
+
+    @staticmethod
+    def fixup_separators(path):
+        if SCons.Platform.platform_default() == "win32":
+            return path.replace(os.path.sep, os.path.altsep)
+        return path
+
+    @staticmethod
+    def fix_path(path):
+        return str(PurePosixPath(Path(path).as_posix()))
+
+    def __call__(self, target, source, env, for_signature):
+        if for_signature:
+            return self.pathobj
+
+        return self.fix_path(env.subst(self.pathobj))
+
+
 def path_as_posix(path):
     if SCons.Platform.platform_default() == "win32":
         return path.replace(os.path.sep, os.path.altsep)