Switch back to runtimeJavaHome for 7.7 feature check

Author: rjernst

x-pack/plugin/build.gradle

@@ -1,7 +1,6 @@
 import org.elasticsearch.gradle.LoggedExec
 import org.elasticsearch.gradle.info.BuildParams
 import org.elasticsearch.gradle.plugin.PluginBuildPlugin
-import org.gradle.internal.jvm.Jvm
 
 import java.nio.charset.StandardCharsets
 
@@ -32,7 +31,7 @@ subprojects {
         dependsOn project.configurations.featureAwarePlugin
         outputs.file(successMarker)
 
-        executable = "${Jvm.current().javaHome}/bin/java"
+        executable = "${BuildParams.runtimeJavaHome}/bin/java"
 
         // default to main class files if such a source set exists
         final List files = []