Use soong_javac_wrapper in soong javac compiles

Test: m checkbuild
Change-Id: I0f9ff0a719ac550a011c2878fc51595dc3427aed
diff --git a/java/config/makevars.go b/java/config/makevars.go
index 1453a07..6b49592 100644
--- a/java/config/makevars.go
+++ b/java/config/makevars.go
@@ -56,4 +56,6 @@
 		ctx.Strict("JLINK", "${JlinkCmd}")
 		ctx.Strict("JMOD", "${JmodCmd}")
 	}
+
+	ctx.Strict("SOONG_JAVAC_WRAPPER", "${SoongJavacWrapper}")
 }