Tries to parse SDKSettings.plist looking for a Catalyst version map, but we
don't currently support this.

--- a/Sources/SwiftDriver/Toolchains/DarwinToolchain.swift
+++ b/Sources/SwiftDriver/Toolchains/DarwinToolchain.swift
@@ -297,11 +297,7 @@ public final class DarwinToolchain: Toolchain {
                                                debugDescription: "Malformed version string")
       }
       self.version = version
-      if self.canonicalName.hasPrefix("macosx") {
-        self.versionMap = try keyedContainer.decode(VersionMap.self, forKey: .versionMap)
-      } else {
         self.versionMap = VersionMap()
-      }
     }