[IDE] Dependency verification of *-sources.jar fails when doing gradle sync

This issue was noticed during review of fix for JDK-8267418
PR: https://github.com/openjdk/jfx/pull/506

When importing OpenJFX project in IntelliJ IDE, IntelliJ downloads and tries to verifiy checksum of several *-sources.jar files. We do not have the checksums for the *-sources.jar files, hence the importing fails.

Gradle provides a way to skip the verification of these jar files: https://docs.gradle.org/current/userguide/dependency_verification.html#sec:skipping-javadocs

We need following change to fix this issue:
diff --git a/gradle/verification-metadata.xml b/gradle/verification-metadata.xml
index abacd0b05b..0a3d33726d 100644
--- a/gradle/verification-metadata.xml
+++ b/gradle/verification-metadata.xml
@@ -3,6 +3,9 @@
    <configuration>
       <verify-metadata>true</verify-metadata>
       <verify-signatures>false</verify-signatures>
+ <trusted-artifacts>
+ <trust file=".*-sources[.]jar" regex="true"/>
+ </trusted-artifacts>
    </configuration>
    <components>
       <component group="" name="ffmpeg-3.3.3" version="">