This patch changes the `Platform::LocateXXX` to return a map from `FileSpec` to `LoadScriptFromSymFile` enum. This is needed for https://github.com/llvm/llvm-project/pull/188722, where I intend to set `LoadScriptFromSymFile` per-module. By default the `Platform::LocateXXX` set the value to whatever the target's current `target.load-script-from-symbol-file` is set to. In https://github.com/llvm/llvm-project/pull/188722 we'll allow overriding this per-target setting on a per-module basis. Drive-by: * Added logging when we fail to load a script.