JavaScriptCore issus were fixed in <https://bugs.webkit.org/show_bug.cgi?id=235734>. The WebCore configuration needs to update its rules for JAVASCRIPTCORE_PRIVATE_HEADERS_DIR to include the system content prefix. The WebKit configuration shouldn't include the system content prefix when computing ALTERNATE_ROOT_PATH (the normal path). It also needs to create the directory where we create the symlink if it doesn't exist. WebKitLegacy fails due to the errors in the other projects.
<rdar://87928380>
Created attachment 450235 [details] Patch
Committed r288749 (246542@trunk): <https://commits.webkit.org/246542@trunk>