I just finished putting together a 7..1.1 amd64 system from source. Unless your i386 system is fast Firefox (57.0.4) takes much longer to build than Friefox52 (esr, 52.5). 57.05 needs to build
lang/clang,
lang/rust and
lang/gcc-49 as dependencies. One the other hand, the 57 release series is faster at rendering pages.