Set metadata sources for Ivy repositories (elastic#41818)

We have faked some Ivy repositories on a few artifact locations. Today
when Gradle attempts to resolve these artifacts, it follows its default
strategy to search for Gradle metadata, then Maven POM files, then Ivy
descriptors, and finally will fallback to looking directly for the
artifact. This wastes times on remote network calls that will 404 anyway
since these metadata resources will not exist for these fake Ivy
repositories. This commit overrides the Gradle strategy to look directly
for artifacts.

distribution/build.gradle

@@ -238,13 +238,19 @@ repositories {
  // simpler legacy pattern from JDK 9 to JDK 12 that we are advocating to Oracle to bring back
  ivy {
  url "https://download.oracle.com"
+ metadataSources {
+ artifact()
+ }
  patternLayout {
  artifact "java/GA/jdk${jdkMajor}/${jdkBuild}/GPL/openjdk-[revision]_[module]-x64_bin.[ext]"
  }
  }
  // current pattern since 12.0.1
  ivy {
  url "https://download.oracle.com"
+ metadataSources {
+ artifact()
+ }
  patternLayout {
  artifact "java/GA/jdk${jdkVersion}/${hash}/${jdkBuild}/GPL/openjdk-[revision]_[module]-x64_bin.[ext]"
  }

qa/wildfly/build.gradle

@@ -38,6 +38,9 @@ repositories {
  // the Wildfly distribution is not available via a repository, so we fake an Ivy repository on top of the download site
  ivy {
  url "https://download.jboss.org"
+ metadataSources {
+ artifact()
+ }
  patternLayout {
  artifact 'wildfly/[revision]/[module]-[revision].[ext]'
  }