Do not set DYLD_LIBRARY_PATH to point the installed toolchain/sdk.

This has not been a good idea since Swift started shipping in the OS. The OS runtime is the one we would like Swift scripts to use. Using the installed toolchain can potentially cause sync issues.

Resolves rdar://78951185

Author: artemcm

Package.resolved

@@ -38,17 +38,9 @@ extension DarwinToolchain {
     targetInfo: FrontendTargetInfo) throws -> [String: String] {
     var envVars: [String: String] = [:]
 
-    let runtimePaths = try runtimeLibraryPaths(
-      for: targetInfo,
-      parsedOptions: &parsedOptions,
-      sdkPath: sdkPath,
-      isShared: true
-    ).map { $0.name }
-
     addPathEnvironmentVariableIfNeeded("DYLD_LIBRARY_PATH", to: &envVars,
                                        currentEnv: env, option: .L,
-                                       parsedOptions: &parsedOptions,
-                                       extraPaths: runtimePaths)
+                                       parsedOptions: &parsedOptions)
 
     addPathEnvironmentVariableIfNeeded("DYLD_FRAMEWORK_PATH", to: &envVars,
                                        currentEnv: env, option: .F,

Sources/SwiftDriver/Jobs/Toolchain+InterpreterSupport.swift

@@ -2338,7 +2338,12 @@ final class SwiftDriverTests: XCTestCase {
       }
 
       XCTAssertFalse(job.commandLine.contains(.flag("--")))
+      // On darwin, swift ships in the OS. Immediate mode should use that runtime.
+      #if os(macOS)
+      XCTAssertFalse(job.extraEnvironment.keys.contains("\(driver.targetTriple.isDarwin ? "DYLD" : "LD")_LIBRARY_PATH"))
+      #else
       XCTAssertTrue(job.extraEnvironment.keys.contains("\(driver.targetTriple.isDarwin ? "DYLD" : "LD")_LIBRARY_PATH"))
+      #endif
     }
 
     do {