boost needs icu as a dep: $ ldd /usr/local/lib/libboost_regex-mt.so
linux-gate.so.1 => (0xb772f000)
libicuuc.so.44 => /usr/local/lib/libicuuc.so.44 (0xb7529000)
libicui18n.so.44 => /usr/local/lib/libicui18n.so.44 (0xb73a9000)
libicudata.so.44 => /usr/local/lib/libicudata.so.44 (0xb6568000)