fix: use --test-dir instead of --build-dir for MSVC ctest step

ctest does not have a --build-dir flag; the correct option to specify
the build directory is --test-dir (available since CMake 3.20).

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: Pierre-Luc Gagné

.github/workflows/ci.yml

@@ -139,4 +139,4 @@ jobs:
         run: cmake --build build --config Release -j4
 
       - name: Unit tests
-        run: ctest --build-dir build -C Release -R tests_unit_ds_mysql --output-on-failure
+        run: ctest --test-dir build -C Release -R tests_unit_ds_mysql --output-on-failure