Fix droiddoc generation.

We want javadoc generated from the standard libraries
we supply and not the host standard libraries.

This also has the side effect of fixing javadoc generation
for java7 APIs that android introduced, while compiling
with java6.

bug: 8992787
Change-Id: Idebc7e12c7743a43b425ef4971f4482719fd480d

core/droiddoc.mk

@@ -52,12 +52,7 @@ LOCAL_DROIDDOC_CUSTOM_ASSET_DIR := assets
 endif
 
 
-$(full_target): PRIVATE_BOOTCLASSPATH :=
-ifeq ($(BUILD_OS),linux)
-# You have to set bootclasspath for javadoc manually on linux since Java 6.
-host_jdk_rt_jar := $(dir $(HOST_JDK_TOOLS_JAR))../jre/lib/rt.jar
-$(full_target): PRIVATE_BOOTCLASSPATH := $(host_jdk_rt_jar)
-endif
+$(full_target): PRIVATE_BOOTCLASSPATH := $(call java-lib-files, core)
 
 ifneq ($(LOCAL_IS_HOST_MODULE),true)
 
@@ -200,6 +195,7 @@ $(full_target): $(full_src_files) $(full_java_lib_deps)
                 -J-Xmx1024m \
                 $(PRIVATE_PROFILING_OPTIONS) \
                 $(addprefix -classpath ,$(PRIVATE_CLASSPATH)) \
+                $(addprefix -bootclasspath ,$(PRIVATE_BOOTCLASSPATH)) \
                 -sourcepath $(PRIVATE_SOURCE_PATH)$(addprefix :,$(PRIVATE_CLASSPATH)) \
                 -d $(PRIVATE_OUT_DIR) \
                 -quiet \