apprt/gtk: Move most version checks to runtime

Unless we are guarding against symbols added in new versions we now
check against the runtime version of GTK to handle them even when we
didn't build against that version.

src/apprt/gtk/App.zig

@@ -111,12 +111,12 @@ pub fn init(core_app: *CoreApp, opts: Options) !App {
     // Disabling Vulkan can improve startup times by hundreds of
     // milliseconds on some systems. We don't use Vulkan so we can just
     // disable it.
-    if (version.atLeast(4, 16, 0)) {
+    if (version.runtimeAtLeast(4, 16, 0)) {
         // From gtk 4.16, GDK_DEBUG is split into GDK_DEBUG and GDK_DISABLE.
         // For the remainder of "why" see the 4.14 comment below.
         _ = internal_os.setenv("GDK_DISABLE", "gles-api,vulkan");
         _ = internal_os.setenv("GDK_DEBUG", "opengl,gl-no-fractional");
-    } else if (version.atLeast(4, 14, 0)) {
+    } else if (version.runtimeAtLeast(4, 14, 0)) {
         // We need to export GDK_DEBUG to run on Wayland after GTK 4.14.
         // Older versions of GTK do not support these values so it is safe
         // to always set this. Forwards versions are uncertain so we'll have to
@@ -138,7 +138,7 @@ pub fn init(core_app: *CoreApp, opts: Options) !App {
         _ = internal_os.setenv("GDK_DEBUG", "vulkan-disable");
     }
 
-    if (version.atLeast(4, 14, 0)) {
+    if (version.runtimeAtLeast(4, 14, 0)) {
         // We need to export GSK_RENDERER to opengl because GTK uses ngl by
         // default after 4.14
         _ = internal_os.setenv("GSK_RENDERER", "opengl");
@@ -1028,7 +1028,7 @@ fn loadRuntimeCss(
         , .{ .font_family = font_family });
     }
 
-    if (version.atLeast(4, 16, 0)) {
+    if (version.runtimeAtLeast(4, 16, 0)) {
         switch (window_theme) {
             .ghostty => try writer.print(
                 \\:root {{