osrm-backend: evade -Werror, fix build (#431628)

pkgs/by-name/os/osrm-backend/package.nix

@@ -45,8 +45,12 @@ stdenv.mkDerivation rec {
     expat
   ];
 
-  # Needed with GCC 12
-  env.NIX_CFLAGS_COMPILE = "-Wno-error=uninitialized";
+  env.NIX_CFLAGS_COMPILE = toString [
+    # Needed with GCC 12
+    "-Wno-error=uninitialized"
+    # Needed with GCC 14
+    "-Wno-error=maybe-uninitialized"
+  ];
 
   postInstall = ''
     mkdir -p $out/share/osrm-backend