charon-xpc: Disable warnings about deprecated functions

This avoids all the deprecated warnings when using OpenSSL functins.

src/frontends/osx/README.md

@@ -25,7 +25,7 @@ the charon-xpc tarball with:
 Before building the Xcode project, the strongSwan base tree must be built using
 a monolithic and static build. This can be achieved on OS X by using:
 
-    CFLAGS="-O2 -Wall -Wno-format -Wno-pointer-sign" \
+    CFLAGS="-O2 -Wall -Wno-format -Wno-pointer-sign -Wno-deprecated-declarations" \
     ./configure --enable-monolithic --disable-shared --enable-static \
         --disable-defaults \
         --enable-openssl --enable-kernel-libipsec --enable-kernel-pfroute \