[Unix] Go back to only checking the runtime resource path for swiftrt.o

Author: finagolfin

Sources/SwiftDriver/Jobs/GenericUnixToolchain+LinkerSupport.swift

@@ -168,16 +168,13 @@ extension GenericUnixToolchain {
       }
 
       if !isEmbeddedEnabled && !parsedOptions.hasArgument(.nostartfiles) {
-        let rsrc: VirtualPath
-        // Prefer the swiftrt.o runtime file from the SDK if it's specified.
-        if let sdk = targetInfo.sdkPath {
-          rsrc = VirtualPath.lookup(sdk.path).appending(components: "usr", "lib", "swift")
-        } else {
-          rsrc = VirtualPath.lookup(targetInfo.runtimeResourcePath.path)
-        }
-        let platform: String = targetTriple.platformName() ?? ""
-        let architecture: String = majorArchitectureName(for: targetTriple)
-        commandLine.appendPath(rsrc.appending(components: platform, architecture, "swiftrt.o"))
+        let swiftrtPath = VirtualPath.lookup(targetInfo.runtimeResourcePath.path)
+          .appending(
+            components: targetTriple.platformName() ?? "",
+            String(majorArchitectureName(for: targetTriple)),
+            "swiftrt.o"
+          )
+        commandLine.appendPath(swiftrtPath)
       }
 
       // If we are linking statically, we need to add all