Buildsystem: More aggressive optimizations

- Enable LTO by default
- Enable Full optimizations by default
- Statically link to libgBar by default

meson.build

@@ -3,7 +3,12 @@ project('gBar',
     version: '0.0.1',
     license: 'MIT',
     meson_version: '>=0.49.0',
-    default_options: ['c_std=c++17', 'warning_level=3'])
+    default_options: ['c_std=c++17',
+                      'warning_level=3',
+                      'default_library=static',
+                      'buildtype=release',
+                      'b_lto=true'],
+)
 
 gtk = dependency('gtk+-3.0')
 gtk_layer_shell = dependency('gtk-layer-shell-0')