builder: add gccWrapper for openwrt < 19

builder.nix

@@ -32,14 +32,25 @@ let
   inherit (import ./files.nix {
     inherit pkgs release target variant sha256 feedsSha256 packagesArch;
   }) arch variantPackages variantFiles feedsPackages;
+
+  gccWrapper = pkgs.runCommand "gcc-wrapper" {} ''
+    mkdir -p $out/bin
+    for i in ${pkgs.gcc.cc}/bin/*-gnu-gcc*; do
+      ln -s ${pkgs.gcc}/bin/gcc $out/bin/$(basename "$i")
+    done
+    for i in ${pkgs.gcc.cc}/bin/*-gnu-{g++,c++}*; do
+      ln -s ${pkgs.gcc}/bin/g++ $out/bin/$(basename "$i")
+    done
+  '';
+
 in
 
 stdenv.mkDerivation {
   name = lib.concatStringsSep "-" ([
     "openwrt" release
-  ] ++
-  lib.optional (extraImageName != null) extraImageName ++
-  [ target variant profile ]);
+  ]
+  ++ lib.optional (extraImageName != null) extraImageName
+  ++ [ target variant profile ]);
 
   src = variantFiles."openwrt-imagebuilder-${release}-${target}-${variant}.${hostPlatform.uname.system}-${hostPlatform.uname.processor}.tar.xz";
 
@@ -65,14 +76,11 @@ stdenv.mkDerivation {
       zlib unzip bzip2
       ncurses which rsync git file getopt wget
       bash perl python3
-    ] ++
-    lib.optional (!lib.versionAtLeast release "21") python2;
+    ]
+    ++ lib.optional (!lib.versionAtLeast release "21") python2
+    ++ lib.optional (!lib.versionAtLeast release "19") gccWrapper;
 
   buildPhase = ''
-    ${lib.optionalString (!lib.versionAtLeast release "19") ''
-      # Hack around broken check for gcc
-      touch staging_dir/host/.prereq-build
-    ''}
     make image SHELL=${runtimeShell} \
       PROFILE="${profile}" \
       PACKAGES="${lib.concatStringsSep " " packages}" \