[gnome-builder] libide/gui: fix checkimage styling

[Christian Hergert <chergert src gnome org>]

commit 3c999555dd059022d72c0bc683d9a57353876c26
Author: Christian Hergert <chergert redhat com>
Date:   Sat Aug 27 22:01:12 2022 -0700

    libide/gui: fix checkimage styling
    
    This is still used apparently, in the build-target selector for instance.

 src/libide/gui/style.css | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)
---
diff --git a/src/libide/gui/style.css b/src/libide/gui/style.css
index 9805817d8..43e0b6cf1 100644
--- a/src/libide/gui/style.css
+++ b/src/libide/gui/style.css
@@ -78,3 +78,19 @@ button.pill.small {
   margin: 0px;
   padding: 3px;
 }
+
+/* Images for checkbuttons in various UI */
+.checkimage radio,
+.checkimage check {
+  background: none;
+  outline: none;
+  box-shadow: none;
+  border: none;
+  color: @window_fg_color;
+  -gtk-icon-source: none;
+  -gtk-icon-size: 18px;
+}
+.checkimage radio:checked,
+.checkimage check:checked {
+  -gtk-icon-source: -gtk-icontheme('object-select-symbolic');
+}