Pass DEXPREOPT_BOOT_JARS_MODULES to Make

Make is not setting PreoptBootJars, pass the value computed in
Soong back to Make.

Test: m checkbuild
Change-Id: Ie3db926df9c5d6bf18db1003b95823c7566800a9
diff --git a/android/variable.go b/android/variable.go
index 700d917..5ee888f 100644
--- a/android/variable.go
+++ b/android/variable.go
@@ -200,8 +200,7 @@
 	UncompressPrivAppDex             *bool    `json:",omitempty"`
 	ModulesLoadedByPrivilegedModules []string `json:",omitempty"`
 
-	BootJars       []string `json:",omitempty"`
-	PreoptBootJars []string `json:",omitempty"`
+	BootJars []string `json:",omitempty"`
 
 	IntegerOverflowExcludePaths []string `json:",omitempty"`