[llvm] [GitHub][CI] Add clang-tidy premerge workflow (PR #154829)

[Baranov Victor via llvm-commits]

================
@@ -0,0 +1,126 @@
+name: "Code lint"
+
+permissions:
+  contents: read
+
+on:
+  pull_request:
+    branches:
+      - main
+      - 'users/**'
+    paths:
+      - 'clang-tools-extra/clang-tidy/**'
+
+jobs:
+  code_linter:
+    if: github.repository_owner == 'llvm'
+    runs-on: ubuntu-24.04
+    defaults:
+      run:
+        shell: bash
----------------
vbvictor wrote:

Error without it:
```console
shell: sh -e {0}
/__w/_temp/17b71f82-c39d-4c08-b74c-e073e04faba2.sh: 2: source: not found
```
So the default is `sh`

https://github.com/llvm/llvm-project/pull/154829