don't clean unless in scheduled run

.gitlab-ci.yml

@@ -59,7 +59,8 @@ windows:
     - cmake -G "Visual Studio 16 2019" -A x64 -T host=x64 -DLIB_MAN=OFF -DQTDIR="$QT_MSVC_DIR" -DQt5_DIR="$QTCMake_DIR/Qt5" -DQt5Test_DIR="$QTCMake_DIR/Qt5Test" -DFFTW3_INCLUDE_DIR="$FFTW3_INCLUDE_DIR" -DFFTW3_LIBRARY="$FFTW3_LIB" -DCMAKE_INCLUDE_PATH="$OPT_DIR/include;$BOOST_INCLUDE_DIR" -DCMAKE_LIBRARY_PATH="$OPT_DIR/lib;$BOOST_LIB_DIR" -DCMAKE_C_COMPILER="cl.exe" -DCMAKE_CXX_COMPILER="cl.exe" -B. ..
     - echo "#--- BUILD ---"
     - pwd
-    - cmake --build . --config Release --clean-first
+    - if($CI_PIPELINE_SOURCE -eq "schedule") { cmake --build . --target clean }
+    - cmake --build . --config Release
     - echo "#--- TEST ---"
     - ctest -C Release --parallel 8 --output-on-failure
     - echo "#--- PACKAGING ---"