Revert "Remove `tool_host_cross_arch_tests` bringup" (#112406)

diff --git a/.ci.yaml b/.ci.yaml
index 601164e..591cba6 100644
--- a/.ci.yaml
+++ b/.ci.yaml
@@ -2843,6 +2843,7 @@
       - .ci.yaml
 
   - name: Mac_x64 tool_host_cross_arch_tests
+    bringup: true # Mac_x64 variant https://github.com/flutter/flutter/pull/109889
     recipe: flutter/flutter_drone
     timeout: 60
     properties:
@@ -2863,6 +2864,7 @@
       - .ci.yaml
 
   - name: Mac_arm64 tool_host_cross_arch_tests
+    bringup: true # Mac_arm64 variant https://github.com/flutter/flutter/pull/109889
     recipe: flutter/flutter_drone
     timeout: 60
     properties: