chore: Update alpha-build.sh script to handle xvfb-run not found and enable LTO only when not cross-compiling

- Add conditional check for xvfb-run command availability
- Enable LTO (Link Time Optimization) only when not cross-compiling

Related recent commits:
- Update Zen Browser styles for dark mode compatibility
- Update Windows mozconfig and ZenWorkspaces.mjs

src/browser/base/content/zenThemeModifier.js

@@ -135,6 +135,9 @@ var ZenThemeModifier = {
     this._updateZenAvatar();
     window.matchMedia('(prefers-color-scheme: dark)').addEventListener('change', this._onPrefersColorSchemeChange.bind(this));
 
+    this._updateTabsToolbar();
+    window.addEventListener("resize", this._onResize.bind(this));
+
     this.closeWatermark();
   },
 
@@ -142,6 +145,19 @@ var ZenThemeModifier = {
     this._updateZenAvatar();
   },
 
+  _onResize(event) {
+    this._updateTabsToolbar();
+  },
+
+  _updateTabsToolbar() {
+    // Set tabs max-height to the "toolbar-items" height
+    const toolbarItems = document.querySelector("#TabsToolbar > .toolbar-items");
+    const tabs = document.getElementById("tabbrowser-arrowscrollbox");
+    const toolbarRect = toolbarItems.getBoundingClientRect();
+    tabs.style.maxHeight = toolbarRect.height - toolbarRect.top + "px";
+    console.log("ZenThemeModifier: set tabs max-height to", toolbarRect.height + "px");
+  },
+
   _updateZenAvatar() {
     const mainWindowEl = document.documentElement;
     // Dont override the sync avatar if it's already set