Error: --enable-application=APP was not Specified and is Required

I tried to compile firefox 3.6.13 ( download source from ftp://ftp.mozilla.org/pub/mozilla.org/firefox/releases/3.6.13/source/ ) according to a former post . I got this error  --enable-application=APP was not specified and is required. After some Googling and looking at this page I added these two lines to my  .mozconfig :
ac_add_options --enable-application=browser
mk_add_options MOZ_CO_PROJECT=browser

It will look like this :
.$topsrcdir/browser/config/mozconfig
mk_add_options MOZ_OBJDIR=@TOPSRCDIR@/ff-release
ac_add_options --disable-debug
ac_add_options --disable-tests
ac_add_options --enable-optimize
ac_add_options --enable-official-branding
ac_add_options --enable-system-cairo
ac_add_options --enable-application=browser
mk_add_options MOZ_CO_PROJECT=browser

After that firefox built fine...