gnuapl: Fix build

One instance of this error/warning comes up during the build.
According to the comment in the code they know what they are doing,
so this can be ignored.

pkgs/development/interpreters/gnu-apl/default.nix

@@ -17,6 +17,8 @@ stdenv.mkDerivation rec {
     "-Wno-error=class-memaccess"
     "-Wno-error=restrict"
     "-Wno-error=format-truncation"
+    # Needed with GCC 10
+    "-Wno-error=maybe-uninitialized"
    ]) ++ optional stdenv.cc.isClang "-Wno-error=null-dereference");
 
   patchPhase = lib.optionalString stdenv.isDarwin ''