[ci] make list of previous releases to download a setting

Co-Authored-By: MarcoFalke <falke.marco@gmail.com>

ci/test/00_setup_env_native_qt5.sh

@@ -14,4 +14,5 @@ export RUN_UNIT_TESTS_SEQUENTIAL="true"
 export RUN_UNIT_TESTS="false"
 export GOAL="install"
 export TEST_PREVIOUS_RELEASES=true
+export PREVIOUS_RELEASES_TO_DOWNLOAD="v0.15.2 v0.16.3 v0.17.1 v0.18.1 v0.19.1"
 export BITCOIN_CONFIG="--enable-zmq --with-gui=qt5 --enable-glibc-back-compat --enable-reduce-exports --enable-c++17 --enable-debug CFLAGS=\"-g0 -O2 -funsigned-char\" CXXFLAGS=\"-g0 -O2 -funsigned-char\""

ci/test/05_before_script.sh

@@ -35,8 +35,8 @@ if [ -z "$NO_DEPENDS" ]; then
   fi
   DOCKER_EXEC $SHELL_OPTS make $MAKEJOBS -C depends HOST=$HOST $DEP_OPTS
 fi
-if [ "$TEST_PREVIOUS_RELEASES" = "true" ]; then
+if [ -n "$PREVIOUS_RELEASES_TO_DOWNLOAD" ]; then
   BEGIN_FOLD previous-versions
-  DOCKER_EXEC contrib/devtools/previous_release.sh -b -t "$PREVIOUS_RELEASES_DIR" v0.15.2 v0.16.3 v0.17.1 v0.18.1 v0.19.1
+  DOCKER_EXEC contrib/devtools/previous_release.sh -b -t "$PREVIOUS_RELEASES_DIR" "${PREVIOUS_RELEASES_TO_DOWNLOAD}"
   END_FOLD
 fi