fix(ci): use Go 1.27 for Darwin backends (#12284)

Older Go linkers stamp pure-Go hosts with SDK metadata that disables
modern Metal APIs. Select Go 1.27 for Darwin builds and document the
backend rebuild requirement.

Assisted-by: Codex:gpt-6

Co-authored-by: localai-org-maint-bot <306269227+localai-org-maint-bot@users.noreply.github.com>

.github/workflows/backend.yml

@@ -355,7 +355,7 @@ jobs:
     with:
       backend: ${{ matrix.backend }}
       build-type: ${{ matrix.build-type }}
-      go-version: "1.25.x"
+      go-version: "1.27.x"
       tag-suffix: ${{ matrix.tag-suffix }}
       lang: ${{ matrix.lang || 'python' }}
       use-pip: ${{ matrix.backend == 'diffusers' }}

.github/workflows/backend_build_darwin.yml

@@ -22,7 +22,8 @@ on:
         type: string
       go-version:
         description: 'Go version to use'
-        default: '1.24.x'
+        # Go 1.27 stamps pure-Go hosts with SDK metadata that supports modern Metal APIs.
+        default: '1.27.x'
         type: string
       tag-suffix:
         description: 'Tag suffix for the built image'

.github/workflows/backend_pr.yml

@@ -281,7 +281,7 @@ jobs:
     with:
       backend: ${{ matrix.backend }}
       build-type: ${{ matrix.build-type }}
-      go-version: "1.25.x"
+      go-version: "1.27.x"
       tag-suffix: ${{ matrix.tag-suffix }}
       lang: ${{ matrix.lang || 'python' }}
       use-pip: ${{ matrix.backend == 'diffusers' }}