Fix typo when building aar

I7dced6acbe621a60cd49daf17872941485602732 introduced a typo,
fix (dir $@) to $(dir $@).

Bug: 64634025
Test: m -j on affected target
Change-Id: Ic7181631630662970337c542b73cd0de6f3f995f
diff --git a/core/static_java_library.mk b/core/static_java_library.mk
index 2a80661..9fcf194 100644
--- a/core/static_java_library.mk
+++ b/core/static_java_library.mk
@@ -209,7 +209,7 @@
 	$(hide) $(foreach res,$(PRIVATE_RESOURCE_DIR),cp -Rfn $(res)/* $(dir $@)aar/res;)
 	$(hide) cp $(PRIVATE_R_TXT) $(dir $@)aar/R.txt
 	$(hide) $(JAR) -cMf $@ \
-	  $(call jar-args-sorted-files-in-directory,(dir $@)aar)
+	  $(call jar-args-sorted-files-in-directory,$(dir $@)aar)
 
 # Register the aar file.
 ALL_MODULES.$(LOCAL_MODULE).AAR := $(built_aar)