Revert of "Lock scratch directory during tool execution" (#7286)

We're seeing hangs in self-hosted jobs since merging this and I can't
repro locally, so let's try this speculative revert to see whether it
resolves the issues.

Reverts #7269

Author: neonichu

Sources/Basics/FileSystem/FileSystem+Extensions.swift

@@ -196,8 +196,8 @@ extension FileSystem {
     }
 
     /// Execute the given block while holding the lock.
-    public func withLock<T>(on path: AbsolutePath, type: FileLock.LockType, blocking: Bool = true, _ body: () throws -> T) throws -> T {
-        try self.withLock(on: path.underlying, type: type, blocking: blocking, body)
+    public func withLock<T>(on path: AbsolutePath, type: FileLock.LockType, _ body: () throws -> T) throws -> T {
+        try self.withLock(on: path.underlying, type: type, body)
     }
 
     /// Returns any known item replacement directories for a given path. These may be used by platform-specific

Sources/CoreCommands/SwiftTool.swift

@@ -41,7 +41,6 @@ import func TSCBasic.exec
 import protocol TSCBasic.OutputByteStream
 import class TSCBasic.Process
 import enum TSCBasic.ProcessEnv
-import enum TSCBasic.ProcessLockError
 import var TSCBasic.stderrStream
 import class TSCBasic.TerminalController
 import class TSCBasic.ThreadSafeOutputByteStream
@@ -109,27 +108,14 @@ extension SwiftCommand {
             workspaceLoaderProvider: self.workspaceLoaderProvider
         )
         swiftTool.buildSystemProvider = try buildSystemProvider(swiftTool)
-
-        // Try a non-blocking lock first so that we can inform the user about an already running SwiftPM.
-        do {
-            try swiftTool.fileSystem.withLock(on: swiftTool.scratchDirectory, type: .exclusive, blocking: false) {}
-        } catch let ProcessLockError.unableToAquireLock(errno) {
-            if errno == EWOULDBLOCK {
-                swiftTool.outputStream.write("Another instance of SwiftPM is already running using '\(swiftTool.scratchDirectory)', waiting until that process has finished execution...".utf8)
-                swiftTool.outputStream.flush()
-            }
-        }
-
         var toolError: Error? = .none
-        try swiftTool.fileSystem.withLock(on: swiftTool.scratchDirectory, type: .exclusive) {
-            do {
-                try self.run(swiftTool)
-                if swiftTool.observabilityScope.errorsReported || swiftTool.executionStatus == .failure {
-                    throw ExitCode.failure
-                }
-            } catch {
-                toolError = error
+        do {
+            try self.run(swiftTool)
+            if swiftTool.observabilityScope.errorsReported || swiftTool.executionStatus == .failure {
+                throw ExitCode.failure
             }
+        } catch {
+            toolError = error
         }
 
         // wait for all observability items to process