Add two new entitlements when debugserver is built by Apple

Two new entitlements, com.apple.private.thread-set-state and
com.apple.private.set-exception-port should be included in the
debugserver entitlement plist when built internally at Apple.
The desktop builds of debugserver don't need these entitlements;
don't add them to debugserver-macosx-entitlements.plist.

rdar://108912676
rdar://103032208