darwin-frameworks: replace cf-private and move it's setup-hook

The only remaining use-case for cf-private are symbols that are not
available in the opensource build.  This generally solved the problem
because of it's setup-hook.

pkgs/os-specific/darwin/apple-sdk/cf-setup-hook.sh

@@ -0,0 +1,9 @@
+linkSystemCoreFoundationFramework() {
+  NIX_CFLAGS_COMPILE="-F@out@/Library/Frameworks $NIX_CFLAGS_COMPILE"
+  # gross! many symbols (such as _OBJC_CLASS_$_NSArray) are defined in system CF, but not
+  # in the opensource release
+  # if the package needs private headers, we assume they also want to link with system CF
+  NIX_LDFLAGS+=" /System/Library/Frameworks/CoreFoundation.framework/Versions/A/CoreFoundation"
+}
+
+preConfigureHooks+=(linkSystemCoreFoundationFramework)