chore: Set timeout for builds on main in post_merge flow to 120 min (#6208)

Signed-off-by: Dmitry Tokarev <dtokarev@nvidia.com>
Co-authored-by: Dillon Cullinan <dcullinan@nvidia.com>

.github/workflows/pr.yaml

@@ -185,6 +185,7 @@ jobs:
         ${{ github.ref_name == 'main' && format('main-vllm-{0}', github.sha) || '' }}
       builder_name: ${{ needs.changed-files.outputs.builder_name }}
       test_gpu_timeout_minutes: 35
+      build_timeout_minutes: ${{ github.ref_name == 'main' && 120 || 60 }}
     secrets: inherit
 
   # ============================================================================
@@ -203,6 +204,7 @@ jobs:
         ${{ github.ref_name == 'main' && 'main-sglang' || '' }}
         ${{ github.ref_name == 'main' && format('main-sglang-{0}', github.sha) || '' }}
       builder_name: ${{ needs.changed-files.outputs.builder_name }}
+      build_timeout_minutes: ${{ github.ref_name == 'main' && 120 || 60 }}
     secrets: inherit
 
   # ============================================================================
@@ -221,6 +223,7 @@ jobs:
         ${{ github.ref_name == 'main' && 'main-trtllm' || '' }}
         ${{ github.ref_name == 'main' && format('main-trtllm-{0}', github.sha) || '' }}
       builder_name: ${{ needs.changed-files.outputs.builder_name }}
+      build_timeout_minutes: ${{ github.ref_name == 'main' && 120 || 60 }}
     secrets: inherit