Remove Java 6 build support

Change-Id: I9754844af58e3f81d7eb9dae286128d17a2cb56c
diff --git a/core/main.mk b/core/main.mk
index 1958a16..b628c8f 100644
--- a/core/main.mk
+++ b/core/main.mk
@@ -139,19 +139,11 @@
 java_version_str := $(shell unset _JAVA_OPTIONS && java -version 2>&1)
 javac_version_str := $(shell unset _JAVA_OPTIONS && javac -version 2>&1)
 
-# Check for the correct version of java, should be 1.7 by
-# default, and 1.6 if LEGACY_USE_JAVA6 is set.
-ifeq ($(LEGACY_USE_JAVA6),)
+# Check for the correct version of java.
 required_version := "1.7.x"
 required_javac_version := "1.7"
 java_version := $(shell echo '$(java_version_str)' | grep '^java .*[ "]1\.7[\. "$$]')
 javac_version := $(shell echo '$(javac_version_str)' | grep '[ "]1\.7[\. "$$]')
-else # if LEGACY_USE_JAVA6
-required_version := "1.6.x"
-required_javac_version := "1.6"
-java_version := $(shell echo '$(java_version_str)' | grep '^java .*[ "]1\.6[\. "$$]')
-javac_version := $(shell echo '$(javac_version_str)' | grep '[ "]1\.6[\. "$$]')
-endif # if LEGACY_USE_JAVA6
 
 ifeq ($(strip $(java_version)),)
 $(info ************************************************************)
@@ -170,13 +162,10 @@
 # Check for the current JDK.
 #
 # For Java 1.7, we require OpenJDK on linux and Oracle JDK on Mac OS.
-# For Java 1.6, we require Oracle for all host OSes.
 requires_openjdk := false
-ifeq ($(LEGACY_USE_JAVA6),)
 ifeq ($(HOST_OS), linux)
 requires_openjdk := true
 endif
-endif
 
 
 # Check for the current jdk