Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.0
Although I also dislike configure's mishandling of LIBS and would like
to see it fixed, I don't think the proposed patch would work well, due
to the funky treatment of LIBS in configure.ac. Please look there for
uses of SAVE_LIBS, pre_PKG_CONFIG_LIBS, PKG_CHECK_MODULES, LIBS_SYSTEM,
LIB_PTHREAD, etc., and note that AC_CHECK_LIB etc. also futz with LIBS.