[epiphany] HACKING.md: recommend --track-origins=yes when running valgrind

[Michael Catanzaro <mcatanzaro src gnome org>]

commit 2a31b3fdc4309bed2a714b9cd015ef355f8e2be5
Author: Michael Catanzaro <mcatanzaro gnome org>
Date:   Fri Mar 20 23:35:36 2020 +0000

    HACKING.md: recommend --track-origins=yes when running valgrind

 HACKING.md | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/HACKING.md b/HACKING.md
index 07a72752e..d267fd34d 100644
--- a/HACKING.md
+++ b/HACKING.md
@@ -215,5 +215,5 @@ To use valgrind, you must use environment variables to disable WebKit's sandbox
 and JavaScriptCore's Gigacage:
 
 ```
-WEBKIT_FORCE_SANDBOX=0 GIGACAGE_ENABLED=0 G_SLICE=always-malloc valgrind epiphany
+WEBKIT_FORCE_SANDBOX=0 GIGACAGE_ENABLED=0 G_SLICE=always-malloc valgrind --track-origins=yes epiphany
 ```