Redirect JVM warnings to stderr in general.

In particular this avoids problems with JVM warnings clashing with the worker protocol, but also matches Blaze's idea of where output goes better.

PiperOrigin-RevId: 524826411
Change-Id: If4c78ac5f63dfd4596da924c12552f6335b8034d

tools/jdk/default_java_toolchain.bzl

@@ -41,6 +41,11 @@ BASE_JDK9_JVM_OPTS = [
 
     # Compact strings make JavaBuilder slightly slower.
     "-XX:-CompactStrings",
+
+    # Since https://bugs.openjdk.org/browse/JDK-8153723, JVM logging goes to stdout. This
+    # makes it go to stderr instead.
+    "-Xlog:disable",
+    "-Xlog:all=warning:stderr:uptime,level,tags",
 ]
 
 JDK9_JVM_OPTS = BASE_JDK9_JVM_OPTS