When you install weex on Ubuntu 18.04 or you build it, it segfaults in line 190 of ftpmain.c. The reason is that host_use_SSL has not been initialized in config.c because the build doesn't set USE_SSL. That's because it is looking for SSL_library_init in libssl, which fails. (nm can't find it either.)
If you change line 36 of configure.in to
AC_CHECK_LIB([ssl],[SSL_connect],
and run
autoconf configure.in > configure
then configure/make produces an executable that works correctly.
I also had to run
autoreconf -vfibefore runningmake. Otherwise I got an error about missingdepcomp. And I had to copyconfig.guessfrom somewhere (e.g. /usr/share/automake-1.15/ on my system).