[geary: 1/2] engine: add missing libm dependency

[Michael Gratton <mjog src gnome org>]

commit 6acddfd02c00edcc8a3a738cfc193131dd170a15
Author: Greg V <greg@unrelenting.technology>
Date:   Thu Apr 11 19:36:19 2019 +0300

    engine: add missing libm dependency
    
    floor() is now used at rfc822-message-data.vala:213 via GLib.Math.floor

 src/engine/meson.build | 1 +
 1 file changed, 1 insertion(+)
---
diff --git a/src/engine/meson.build b/src/engine/meson.build
index 0e43860a..c9b049c9 100644
--- a/src/engine/meson.build
+++ b/src/engine/meson.build
@@ -327,6 +327,7 @@ geary_engine_sources = [
 ]
 
 geary_engine_dependencies = [
+  libmath,
   gee,
   gio,
   glib,