ci: flatten curl-for-win Windows artifact

This logic would be more involved for non-Windows operating systems,
in case we want to deploy such for trurl.

The `find ... -execdir mv ...` command must execute inside the docker
machine, otherwise this happens:
```
mv: cannot move './libcurl.dll' to '../libcurl.dll': Permission denied
mv: cannot move './trurl.exe' to '../trurl.exe': Permission denied
```
Ref: https://github.com/curl/trurl/actions/runs/6825013239/job/18562030977#step:3:9083

Perhaps a 'flat package' option in curl-for-win could resolve this
for all targets better in the future.

.github/workflows/curl-for-win.yml

@@ -44,7 +44,9 @@ jobs:
             --env-file <(env | grep -a -E \
               '^(CW_|GITHUB_)') \
             "${DOCKER_IMAGE}" \
-            sh -c ./_ci-linux-debian.sh
+            sh -c \
+              './_ci-linux-debian.sh;
+              find curl-*-*-mingw* \( -name trurl.exe -o -name "libcurl*.dll" \) -execdir mv -- {} .. \;'
 
       - name: 'list dependencies'
         run: cat urls.txt
@@ -54,5 +56,5 @@ jobs:
           name: 'trurl-windows-llvm'
           retention-days: 5
           path: |
-            curl-*-*-mingw*/bin/trurl.exe
-            curl-*-*-mingw*/bin/libcurl*.dll
+            curl-*-*-mingw*/trurl.exe
+            curl-*-*-mingw*/libcurl*.dll