Ignore discarded restrict qualifiers.

Python-cffi may discard these but they should still work in practice.
This might accidentally ignore const discards too, but I've only added
this flag to releases for now.

Author: HexDecimal

build_libtcod.py

@@ -320,6 +320,7 @@ def fix_header(filepath: str) -> None:
         "-g",
         "-fPIC",
         "-Wno-deprecated-declarations",
+        "-Wno-discarded-qualifiers",  # Ignore discarded restrict qualifiers.
     ],
 }