Put .profile section values in quotes if not alphanumeric

This is supposed to be sourcable by shells so make sure we use
quotes in case values with whitespace are used.

mkosi/__init__.py

@@ -2011,6 +2011,9 @@ def build_uki_profiles(context: Context, cmdline: Sequence[str]) -> list[Path]:
 
  with profile_section.open("w") as f:
  for k, v in profile.profile.items():
+ if not all(c.isalnum() for c in v):
+ v = f'"{v}"'
+
  f.write(f"{k}={v}\n")
 
  with complete_step(f"Generating UKI profile '{id}'"):