Don't dexpreopt when compile_dex but not installable

Modules shouldn't be dexpreopted and possibly stripped when
compile_dex is set but installable is not set.  This matches the
previous behavior when the dexpreopt rules were in Make.

Bug: 121317615
Test: dexpreopt_test.go
Change-Id: I6f80b7b37a990c475b91aa5d98a19a3baa85eb1b
diff --git a/java/java.go b/java/java.go
index 12e724e..5e67193 100644
--- a/java/java.go
+++ b/java/java.go
@@ -1326,6 +1326,7 @@
 
 		j.dexJarFile = dexOutputFile
 
+		j.dexpreopter.isInstallable = Bool(j.properties.Installable)
 		dexOutputFile = j.dexpreopt(ctx, dexOutputFile)
 
 		j.maybeStrippedDexJarFile = dexOutputFile