Revert "Use java prebuilts"

This reverts commit 193175094081e9cc3c44e2b3ee290195b1b89613.

Change-Id: I7a99fd6c53d35a2a674f2d60b113a727f3c453ce
diff --git a/core/combo/javac.mk b/core/combo/javac.mk
index 6d05e06..5c2668c 100644
--- a/core/combo/javac.mk
+++ b/core/combo/javac.mk
@@ -16,20 +16,16 @@
 
 common_jdk_flags := -Xmaxerrs 9999999
 
-ANDROID_JAVA_HOME := prebuilts/jdk/jdk8/$(HOST_PREBUILT_TAG)
-ANDROID_JAVA_TOOLCHAIN := $(ANDROID_JAVA_HOME)/bin
-export JAVA_HOME := $(ANDROID_JAVA_HOME)
-
 # Use the indexer wrapper to index the codebase instead of the javac compiler
 ifeq ($(ALTERNATE_JAVAC),)
-JAVACC := $(ANDROID_JAVA_TOOLCHAIN)/javac
+JAVACC := javac
 else
 JAVACC := $(ALTERNATE_JAVAC)
 endif
 
-JAVA := $(ANDROID_JAVA_TOOLCHAIN)/java
-JAVADOC := $(ANDROID_JAVA_TOOLCHAIN)/javadoc
-JAR := $(ANDROID_JAVA_TOOLCHAIN)/jar
+JAVA := java
+JAVADOC := javadoc
+JAR := jar
 
 # The actual compiler can be wrapped by setting the JAVAC_WRAPPER var.
 ifdef JAVAC_WRAPPER
@@ -38,8 +34,16 @@
     endif
 endif
 
+# Whatever compiler is on this system.
 COMMON_JAVAC := $(JAVACC) -J-Xmx2048M $(common_jdk_flags)
 
+# Eclipse.
+ifeq ($(CUSTOM_JAVA_COMPILER), eclipse)
+    COMMON_JAVAC := java -Xmx256m -jar prebuilt/common/ecj/ecj.jar -5 \
+        -maxProblems 9999999 -nowarn
+    $(info CUSTOM_JAVA_COMPILER=eclipse)
+endif
+
 GLOBAL_JAVAC_DEBUG_FLAGS := -g
 
 HOST_JAVAC ?= $(COMMON_JAVAC)