fixed documetation on hardening flags

Author: haltingstate

doc/build-unix.md

@@ -140,7 +140,10 @@ To help make your bitcoin installation more secure by making certain attacks imp
 exploit even if a vulnerability is found, binaries are hardened by default.
 This can be disabled with:
 
-./configure --enable-hardening
+Hardening Flags:
+
+	./configure --enable-hardening
+	./configure --disable-hardening
 
 
 Hardening enables the following features: