Set PACKAGER in autobuild directly

Instead of depending on the caller to set it.

.github/workflows/build.yml

@@ -148,7 +148,6 @@ jobs:
         GITHUB_TOKEN_READONLY: ${{ secrets.GITHUBTOKENREADONLY }}
         GITHUB_RUN_NAME: ${{ matrix.name }}
       run: |
-        $env:PACKAGER='CI (msys2-autobuild/' + $env:GITHUB_SHA.Substring(0, 8) + '/' + $env:GITHUB_RUN_ID + ')'
         $BUILD_ROOT='C:\'
         $MSYS2_ROOT=(msys2 -c 'cygpath -w /')
         python -u autobuild.py build ${{ matrix.build-args }} "$MSYS2_ROOT" "$BUILD_ROOT"

autobuild.py

@@ -473,7 +473,15 @@ SigLevel=Never
 
 
 def get_build_environ() -> Dict[str, str]:
-    return os.environ.copy()
+    environ = os.environ.copy()
+
+    # Set PACKAGER for makepkg
+    packager_ref = Config.MAIN_REPO
+    if "GITHUB_SHA" in environ and "GITHUB_RUN_ID" in environ:
+        packager_ref += "/" + environ["GITHUB_SHA"][:8] + "/" + environ["GITHUB_RUN_ID"]
+    environ["PACKAGER"] = f"CI ({packager_ref})"
+
+    return environ
 
 
 def build_package(build_type: BuildType, pkg: Package, msys2_root: _PathLike, builddir: _PathLike) -> None: