[clang] [Clang][Darwin] Centralize framework search paths for headers & libraries. (PR #118543)

[Cyndy Ishida via cfe-commits]

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@@ -150,3 +150,23 @@ clang::parseDarwinSDKInfo(llvm::vfs::FileSystem &VFS, StringRef SDKRootPath) {
   return llvm::make_error<llvm::StringError>("invalid SDKSettings.json",
                                              llvm::inconvertibleErrorCode());
 }
+
+// For certain platforms/environments almost all resources (e.g., headers) are
+// located in sub-directories, e.g., for DriverKit they live in
+// <SYSROOT>/System/DriverKit/usr/include (instead of <SYSROOT>/usr/include).
+StringRef clang::getSystemPrefix(const llvm::Triple &T) {
+  if (T.isDriverKit())
+    return "/System/DriverKit";
+  return "";
+}
+
+KnownSystemPaths clang::getCommonSystemPaths(llvm::Triple T) {
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cyndyishida wrote:

yeah, I was initially thinking any common paths between header & linker search which in practice is only frameworks but could be extended in the future. That feels unlikely though. I can apply your suggestion, assuming it's still relevant, after rebasing your patch. 

https://github.com/llvm/llvm-project/pull/118543