fix source root locations.

These have changed following commit
c3255fe8ec.

See also:

- https://github.com/NixOS/nixpkgs/pull/31004
- https://github.com/NixOS/nixpkgs/pull/31106

pkgs/development/tools/build-managers/icmake/default.nix

@@ -11,7 +11,10 @@ stdenv.mkDerivation rec {
     owner = "fbb-git";
   };
 
-  sourceRoot = "icmake-${version}-src/icmake";
+
+  setSourceRoot = ''
+    sourceRoot=$(echo */icmake)
+  '';
 
   buildInputs = [ gcc ];