Make javac checkbuilds match jack

Building all java to dex is very slow.  Make javac checkbuilds act
like jack checkbuilds and only build to class files for unused
modules, and add a java-dex target that can be used to build
everything to dex.

Test: m -j checkbuild
Change-Id: Idcf9c9e0223b9dd88aaa53beb0cb50a230034b0f
diff --git a/core/java.mk b/core/java.mk
index f6c66d5..ed05484 100644
--- a/core/java.mk
+++ b/core/java.mk
@@ -346,11 +346,7 @@
 LOCAL_CHECKED_MODULE := $(jack_check_timestamp)
 endif
 else
-ifeq ($(LOCAL_IS_STATIC_JAVA_LIBRARY),true)
 LOCAL_CHECKED_MODULE := $(full_classes_compiled_jar)
-else
-LOCAL_CHECKED_MODULE := $(built_dex)
-endif
 endif
 endif
 endif
@@ -663,6 +659,8 @@
 	$(hide) rm -f $(dir $@)/classes*.dex
 	$(hide) cp -fp $(dir $<)/classes*.dex $(dir $@)
 
+java-dex: $(built_dex)
+
 endif # !LOCAL_IS_STATIC_JAVA_LIBRARY
 
 findbugs_xml := $(intermediates.COMMON)/findbugs.xml