Do not fail unit test due to gdb abbreviating strings

Do not fail unit test due to gdb abbreviating strings

gdb by default will only print strings up to 200 characters. After that
it abbreviates them. This affects the run-assert-msg-test.sh script if
the path to the glib installation is too long (in our case it was 133
characters, 132 would still have worked...)

By having gdb execute "set print elements 0" before printing the assert
string, the limit on maximum number of characters to print is set to
unlimited.

Signed-off-by: Peter Kjellerstedt <pkj@axis.com>
https://bugzilla.gnome.org/show_bug.cgi?id=670218