Suppress Gradle's welcome message in CI builds

Closes gh-19630

ci/scripts/build-project-windows.bat

@@ -1,4 +1,4 @@
 SET "JAVA_HOME=C:\opt\jdk-8"
 SET PATH=%PATH%;C:\Program Files\Git\usr\bin
 cd git-repo
-.\gradlew --no-daemon --max-workers=4 build
+.\gradlew --no-daemon --max-workers=4 --quiet build

ci/scripts/build-project.sh

@@ -5,5 +5,5 @@ source $(dirname $0)/common.sh
 repository=$(pwd)/distribution-repository
 
 pushd git-repo > /dev/null
-./gradlew --no-daemon --max-workers=4 -PdeploymentRepository=${repository} build publishAllPublicationsToDeploymentRepository
+./gradlew --no-daemon --max-workers=4 --quiet -PdeploymentRepository=${repository} build publishAllPublicationsToDeploymentRepository
 popd > /dev/null