sonar permits to decide when to compile

the new default behavior of sonarscanner is to not compile any more,
to permit easier re-run. it can be controlled by a flag. the default
behavior changes from sonar 4.4.1 to sonar 5.0.0. the name of the flag
is unlucky. see here for more explanation:
https://community.sonarsource.com/t/sonarscanner-for-gradle-you-can-now-decide-when-to-compile

templates/gradle.properties

@@ -7,6 +7,11 @@ org.gradle.parallel=false
 org.gradle.configureondemand=false
 org.gradle.jvmargs=-Xmx1024m
 
+# from sonar-5 onwards sonar does not compile any more. instead of "gradle sonar" one needs to call
+# "gradle assemble sonar".
+# see https://community.sonarsource.com/t/sonarscanner-for-gradle-you-can-now-decide-when-to-compile
+systemProp.sonar.gradle.skipCompile=true
+
 # This prevents the generic Maven publish from publishing sha files - https://github.com/gradle/gradle/issues/11308
 # systemProp.org.gradle.internal.publish.checksums.insecure=true
 # To pass via CLI use: -Dorg.gradle.internal.publish.checksums.insecure=true