furnace, tvheadend: more fallout from gcc upgrade

pkgs/applications/audio/furnace/default.nix

@@ -63,8 +63,8 @@ stdenv.mkDerivation rec {
     "-DWARNINGS_ARE_ERRORS=ON"
   ];
 
-  NIX_CFLAGS_COMPILE = lib.optionals stdenv.cc.isGNU [
-    # Needed with GCC 12 but breaks on darwin (with clang)
+  NIX_CFLAGS_COMPILE = lib.optionals (stdenv.cc.isGNU && lib.versionAtLeast stdenv.cc.version "12") [
+    # Needed with GCC 12 but breaks on darwin (with clang) or aarch64 (old gcc)
     "-Wno-error=mismatched-new-delete"
     "-Wno-error=use-after-free"
   ];

pkgs/servers/tvheadend/default.nix

@@ -78,7 +78,8 @@ in stdenv.mkDerivation {
   NIX_CFLAGS_COMPILE = [
     "-Wno-error=format-truncation"
     "-Wno-error=stringop-truncation"
-    # Needed with GCC 12
+  ] ++ lib.optionals (stdenv.cc.isGNU && lib.versionAtLeast stdenv.cc.version "12") [
+    # Needed with GCC 12 but unrecognized with GCC 9
     "-Wno-error=use-after-free"
   ];