gcc: neverbuild, Buildroot can rebuild it :-)

build

@@ -112,8 +112,7 @@ so looping over all of them would waste time.
             },
             submodules_shallow = {
                 'binutils-gdb',
-                # https://stackoverflow.com/questions/54992977/how-to-select-an-override-srcdir-source-for-gcc-when-building-buildroot
-                # 'gcc',
+                'gcc',
                 'glibc',
             },
             # https://buildroot.org/downloads/manual/manual.html#requirement