Replace -classpath with --class-loader-context for preopt

Use --class-loader-context to pass the context to dex2oat instead of using
runtime arguments.

In preparation to simplify dex2oat handling of contexts.

Bug: 38138251
Test: make & check that the prebuilds have '&' as their classpath key
Change-Id: Iad2fc4364173f59f41886556222ec69f87a0bd52
diff --git a/core/dex_preopt_libart.mk b/core/dex_preopt_libart.mk
index 47fdba6..0f2bb86 100644
--- a/core/dex_preopt_libart.mk
+++ b/core/dex_preopt_libart.mk
@@ -11,9 +11,9 @@
 DEX2OAT := $(HOST_OUT_EXECUTABLES)/dex2oatd$(HOST_EXECUTABLE_SUFFIX)
 endif
 
-# Pass special classpath to skip uses library check.
+# Pass special class loader context to skip the classpath and collision check.
 # Should modify build system to pass used libraries properly later.
-DEX2OAT_CLASSPATH := "&"
+DEX2OAT_CLASS_LOADER_CONTEXT := "&"
 
 DEX2OAT_DEPENDENCY += $(DEX2OAT)
 
@@ -146,7 +146,7 @@
 $(hide) mkdir -p $(dir $(2))
 $(hide) ANDROID_LOG_TAGS="*:e" $(DEX2OAT) \
 	--runtime-arg -Xms$(DEX2OAT_XMS) --runtime-arg -Xmx$(DEX2OAT_XMX) \
-	--runtime-arg -classpath --runtime-arg $(DEX2OAT_CLASSPATH) \
+	--class-loader-context=$(DEX2OAT_CLASS_LOADER_CONTEXT) \
 	--boot-image=$(PRIVATE_DEX_PREOPT_IMAGE_LOCATION) \
 	--dex-file=$(1) \
 	--dex-location=$(PRIVATE_DEX_LOCATION) \