OK, fair enough. But that dumps core too, in different ways depending on whether I try it with the dbg binary or the version in the build directory:

[sbox-FREMANTLE_X86: ~] > run-standalone.sh /usr/lib/debug/usr/bin/modest
/usr/bin/run-standalone.sh: line 11: 14199 Illegal instruction (core dumped) "$@"

[sbox-FREMANTLE_X86: ~/modest/modest/modest-3.1.18+0m5/src] > run-standalone.sh ./modest
/usr/bin/run-standalone.sh: line 11: 14182 Segmentation fault (core dumped) "$@"