.github/workflows/nano-server: test ucrt64/bin instead of mingw64/bin

The nano-server smoke test mounts the SDK's per-arch `bin/` into a
container and runs `git.exe` from there. With the SDK now flipping
over to UCRT64, the path under the working tree is `ucrt64/bin/`
rather than `mingw64/bin/`. The check on `main` (and on every other
ucrt64-branch push so far) succeeded only because the mingw64 tree was
still present; the latest push removed it and the next nano-server
run failed with "bind source path does not exist: ...\mingw64\bin",
which this fixes.

Assisted-by: Opus 4.7
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>

Author: dscho

.github/workflows/nano-server.yml

@@ -18,7 +18,7 @@ jobs:
           # cannot use `git clone` directly, to allow for PR's refs to be fetched
           git clone --no-checkout --single-branch -b ${REF#refs/heads/} --filter=blob:none --depth=1 \
             https://github.com/${{github.repository}} . &&
-          git sparse-checkout set .github/workflows mingw64/bin &&
+          git sparse-checkout set .github/workflows ucrt64/bin &&
           git checkout HEAD
       - name: pull nanoserver image
         shell: bash
@@ -30,6 +30,6 @@ jobs:
           docker run \
             --user "ContainerAdministrator" \
             -v "$WINDBG_DIR:C:/dbg" \
-            -v "$(cygpath -aw mingw64/bin):C:/test" \
+            -v "$(cygpath -aw ucrt64/bin):C:/test" \
             -v "$(cygpath -aw .github/workflows/nano-server):C:/script" \
             $IMAGE pwsh.exe C:/script/run-tests.ps1