Revert "TO-DROP: reuse msys2-runtime build artifact from earlier run"

I actually need to rebuild it because of the backport of 65a48c7202
(Cygwin: console: Call set_input_mode() after changing
disable_master_thread, 2025-07-03).

Signed-off-by: Johannes Schindelin <[email protected]>

Author: dscho

.github/workflows/build.yaml

@@ -6,7 +6,40 @@ permissions:
   contents: read
 
 jobs:
+  build:
+    runs-on: windows-latest
+
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v4
+
+      - name: setup-msys2
+        uses: msys2/setup-msys2@v2
+        with:
+          msystem: MSYS
+          update: true
+          install: msys2-devel base-devel autotools cocom diffutils gcc gettext-devel libiconv-devel make mingw-w64-cross-crt mingw-w64-cross-gcc mingw-w64-cross-zlib perl zlib-devel xmlto docbook-xsl
+
+      - name: Build
+        shell: msys2 {0}
+        run: |
+          (cd winsup && ./autogen.sh)
+          ./configure --disable-dependency-tracking --with-msys2-runtime-commit="$GITHUB_SHA"
+          make -j8
+
+      - name: Install
+        shell: msys2 {0}
+        run: |
+          make DESTDIR="$(pwd)"/_dest install
+
+      - name: Upload
+        uses: actions/upload-artifact@v4
+        with:
+          name: install
+          path: _dest/
+
   ui-tests:
+    needs: build
     uses: ./.github/workflows/ui-tests.yml
     with:
       msys2-runtime-artifact-name: install

.github/workflows/ui-tests.yml

@@ -25,9 +25,6 @@ jobs:
     steps:
       - uses: actions/download-artifact@v4
         with:
-          github-token: ${{ secrets.GITHUB_TOKEN }}
-          repository: dscho/msys2-runtime
-          run-id: 16068904493
           name: ${{ inputs.msys2-runtime-artifact-name }}
           path: ${{ runner.temp }}/artifacts
       - name: replace MSYS2 runtime