Actually use the mtxstatic variable in ci script

.ci/script.sh

@@ -28,7 +28,8 @@ fi
 cmake -GNinja -Hdeps -B.deps \
     -DUSE_BUNDLED_BOOST="${USE_BUNDLED_BOOST}" \
     -DUSE_BUNDLED_CMARK="${USE_BUNDLED_CMARK}" \
-    -DUSE_BUNDLED_JSON="${USE_BUNDLED_JSON}"
+    -DUSE_BUNDLED_JSON="${USE_BUNDLED_JSON}" \
+    -DMTX_STATIC="${MTX_STATIC:-OFF}"
 cmake --build .deps
 
 # Build nheko