engine: add missing libm dependency
Because floor()
is now used at rfc822-message-data.vala:213
via GLib.Math.floor
:
ld: error: undefined symbol: floor
>>> referenced by rfc822-message-data.vala:213 (../src/engine/rfc822/rfc822-message-data.vala:213)
>>> meson-generated_rfc822_rfc822-message-data.c.o:(geary_rf_c822_date_to_rfc822_string) in archive src/engine/libgeary-engine.a
cc: error: linker command failed with exit code 1 (use -v to see invocation)