Revert "Revert "Add soong_javac_filter to all javac commands""

This reverts commit 52d2253ff9617e0c1ad767274e8627c39776198a.

Test: pipe the grok build output through soong_javac_filter
Change-Id: I449a61ed2c95b3e1afd51a31a11baab15d97e2f2
diff --git a/core/config.mk b/core/config.mk
index 0cf1293..503be2f 100644
--- a/core/config.mk
+++ b/core/config.mk
@@ -497,6 +497,8 @@
 SOONG_ZIP := $(SOONG_HOST_OUT_EXECUTABLES)/soong_zip
 ZIP2ZIP := $(SOONG_HOST_OUT_EXECUTABLES)/zip2zip
 
+JAVAC_FILTER := $(SOONG_HOST_OUT_EXECUTABLES)/soong_javac_filter
+
 # Always use prebuilts for ckati and makeparallel
 prebuilt_build_tools := prebuilts/build-tools
 ifeq ($(filter address,$(SANITIZE_HOST)),)