Build with java7 by default.

All introduce a flag LEGACY_USE_JAVA6 to force java6 builds.
This is an unsupported configuration, and provided temporarily
to iron out regressions and compare build output (if required.).

- Increment the version check sequence number.
- Move a more specific check (OpenJDK vs non OpenJDK) after
  the more general version check.
- Update the link in the version check error message to the
  "initializing" page instead of the "download" page. The latter
  talks about repo, mainly.

bug: 8992787

Change-Id: I313e17b1911768d4f3bc318c4162c53dec6eaf0d
diff --git a/core/config.mk b/core/config.mk
index acbf94a..8290f9a 100644
--- a/core/config.mk
+++ b/core/config.mk
@@ -362,7 +362,7 @@
 OLD_FLEX := prebuilts/misc/$(HOST_PREBUILT_TAG)/flex/flex-2.5.4a$(HOST_EXECUTABLE_SUFFIX)
 
 ifeq ($(HOST_OS),darwin)
-ifneq ($(EXPERIMENTAL_USE_JAVA7),)
+ifeq ($(LEGACY_USE_JAVA6),)
 HOST_JDK_TOOLS_JAR:= $(shell $(BUILD_SYSTEM)/find-jdk-tools-jar.sh)
 else
 # Deliberately set to blank for Java 6 installations on MacOS. These