grsecurity: enable PAX_INITIFY

Uses gcc plugin to detect more instances where memory used during init
can be freed.

pkgs/os-specific/linux/kernel/grsecurity-nixos-config.nix

@@ -22,6 +22,10 @@ PAX_PT_PAX_FLAGS y
 PAX_XATTR_PAX_FLAGS y
 PAX_EI_PAX n
 
+PAX_INITIFY y
+# initify is a fairly recent feature, enable verbose mode to aid in debugging
+PAX_INITIFY_VERBOSE y
+
 # The bts instrumentation method is compatible with binary only modules.
 #
 # Note: if platform supports SMEP, we could do without this