[Caching] Remove the error for creating multiple CAS at same location

Remove the CASError that prevents creating two different CAS at the same
CAS path. This allows build system to create compatible CAS at the same
location even the configuration is slightly different.

Author: cachemeifyoucan

Sources/SwiftDriver/ExplicitModuleBuilds/InterModuleDependencies/InterModuleDependencyOracle.swift

@@ -189,12 +189,6 @@ public class InterModuleDependencyOracle {
       if let cas = createdCASMap[casOpt] {
         return cas
       }
-      if let path = onDiskPath {
-        guard !seenCASPath.contains(path) else {
-          throw DependencyScanningError.casError("Cannot create two different CAS at the same OnDiskPath")
-        }
-        seenCASPath.insert(path)
-      }
       let cas = try swiftScan.createCAS(pluginPath: pluginPath?.pathString, onDiskPath: onDiskPath?.pathString, pluginOptions: pluginOptions)
       createdCASMap[casOpt] = cas
       return cas
@@ -234,7 +228,5 @@ public class InterModuleDependencyOracle {
 
   /// Storing the CAS created via CASConfig.
   internal var createdCASMap: [CASConfig: SwiftScanCAS] = [:]
-  /// The on disk path seen by CAS creation function.
-  internal var seenCASPath: Set<AbsolutePath> = []
 }