Allow disabling turbine

m -j TURBINE_ENABLED=false will build without turbine.  This is
primarily useful for A/B comparisions of turbine builds, but will
also be used to temporarily disable turbine for unbundled builds
until we have turbine prebuilts.

Bug: 64308460
Test: m -j TURBINE_ENABLED=false java
Test: m -j java
Change-Id: Ie48746c8bfc60c361be9634cb1805ca1c09aa1fe
diff --git a/core/soong_java_prebuilt.mk b/core/soong_java_prebuilt.mk
index ce09eb1..9198d68 100644
--- a/core/soong_java_prebuilt.mk
+++ b/core/soong_java_prebuilt.mk
@@ -26,11 +26,13 @@
 
 $(eval $(call copy-one-file,$(LOCAL_FULL_CLASSES_JACOCO_JAR),$(full_classes_jar)))
 
+ifneq ($(TURBINE_DISABLED),false)
 ifdef LOCAL_SOONG_HEADER_JAR
 $(eval $(call copy-one-file,$(LOCAL_SOONG_HEADER_JAR),$(full_classes_header_jar)))
 else
 $(eval $(call copy-one-file,$(full_classes_jar),$(full_classes_header_jar)))
 endif
+endif # TURBINE_DISABLED != false
 
 ifdef LOCAL_SOONG_DEX_JAR
 $(eval $(call copy-one-file,$(LOCAL_SOONG_DEX_JAR),$(common_javalib.jar)))