factor-lang: fix upgrade to include changes from 8d999d4

pkgs/development/compilers/factor-lang/factor99.nix

···
       done)> $out/lib/factor/ld.so.cache
 
     make -j$NIX_BUILD_CORES linux-x86-64
+    printf "First build from upstream boot image\n" >&2
+    ./build.sh bootstrap
+    printf "Rebuild boot image\n" >&2
+    ./factor -script -e='"unix-x86.64" USING: system bootstrap.image memory ; make-image save 0 exit'
+    printf "Second build from local boot image\n" >&2
     ./build.sh bootstrap
     runHook postBuild
   '';
···
     license = licenses.bsd2;
     maintainers = with maintainers; [ vrthra spacefrogg ];
     platforms = lib.intersectLists platforms.x86_64 platforms.linux;
+    mainProgram = "factor";
   };
 }