Add .exe to Windows binaries

Author: gmittert

Sources/Workspace/UserToolchain.swift

@@ -19,6 +19,11 @@ private let whichArgs: [String] = ["xcrun", "--find"]
 #else
 private let whichArgs = ["which"]
 #endif
+#if os(Windows)
+private let hostExecutableSuffix = ".exe"
+#else
+private let hostExecutableSuffix = ""
+#endif
 
 /// Concrete object for manifest resource provider.
 public struct UserManifestResources: ManifestResourceProvider {
@@ -56,7 +61,7 @@ public final class UserToolchain: Toolchain {
 
     /// Path of the `swift` interpreter.
     public var swiftInterpreter: AbsolutePath {
-        return swiftCompiler.parentDirectory.appending(component: "swift")
+        return swiftCompiler.parentDirectory.appending(component: "swift" + hostExecutableSuffix)
     }
 
     /// Path to the xctest utility.
@@ -97,7 +102,7 @@ public final class UserToolchain: Toolchain {
         func validateCompiler(at path: AbsolutePath?) throws {
             guard let path = path else { return }
             guard localFileSystem.isExecutableFile(path) else {
-                throw InvalidToolchainDiagnostic("could not find the `swiftc` at expected path \(path)")
+                throw InvalidToolchainDiagnostic("could not find the `swiftc\(hostExecutableSuffix)` at expected path \(path)")
             }
         }
 
@@ -112,13 +117,13 @@ public final class UserToolchain: Toolchain {
         // We require there is at least one valid swift compiler, either in the
         // bin dir or SWIFT_EXEC.
         let resolvedBinDirCompiler: AbsolutePath
-        let binDirCompiler = binDir.appending(component: "swiftc")
+        let binDirCompiler = binDir.appending(component: "swiftc" + hostExecutableSuffix)
         if localFileSystem.isExecutableFile(binDirCompiler) {
             resolvedBinDirCompiler = binDirCompiler
         } else if let SWIFT_EXEC = SWIFT_EXEC {
             resolvedBinDirCompiler = SWIFT_EXEC
         } else {
-            throw InvalidToolchainDiagnostic("could not find the `swiftc` at expected path \(binDirCompiler)")
+            throw InvalidToolchainDiagnostic("could not find the `swiftc\(hostExecutableSuffix)` at expected path \(binDirCompiler)")
         }
 
         // The compiler for compilation tasks is SWIFT_EXEC or the bin dir compiler.
@@ -207,7 +212,7 @@ public final class UserToolchain: Toolchain {
         self.swiftCompiler = swiftCompilers.compile
 
         // Look for llbuild in bin dir.
-        llbuild = binDir.appending(component: "swift-build-tool")
+        llbuild = binDir.appending(component: "swift-build-tool" + hostExecutableSuffix)
         guard localFileSystem.exists(llbuild) else {
             throw InvalidToolchainDiagnostic("could not find `llbuild` at expected path \(llbuild)")
         }