build(grantlee): honor DISABLE_TESTS env to disable BUILD_TESTING during CMake configure

app/build_grantlee_qt6.sh

@@ -86,7 +86,8 @@ mkdir -p grantlee/build
 cd grantlee/build
 cmake -DCMAKE_BUILD_TYPE=Release \
       -DCMAKE_INSTALL_PREFIX="${INSTALL_PREFIX}" \
-      -DCMAKE_PREFIX_PATH="${QT_ROOT}:${INSTALL_PREFIX}" ..
+      -DCMAKE_PREFIX_PATH="${QT_ROOT}:${INSTALL_PREFIX}" \
+      ${DISABLE_TESTS:+-DBUILD_TESTING=OFF} ..
 
 cmake --build . -- -j$(nproc) || true
 cmake --install . || true