[Build] Add destination to the build parameters

`BuildParameters` could either be used for `host` to `target`
builds, add an ability to indicate that and switch `suffix`
to use that information instead of requiring triple to be
passed in. This helps avoid mismatches and makes it harder
to mix us parameter's intended use.

Author: xedin

Sources/Build/BuildDescription/ResolvedModule+BuildDescription.swift

@@ -17,7 +17,7 @@ import SPMBuildCore
 
 extension ResolvedModule {
     func tempsPath(_ buildParameters: BuildParameters) -> AbsolutePath {
-        let suffix = buildParameters.suffix(triple: self.buildTriple)
+        let suffix = buildParameters.suffix
         return buildParameters.buildPath.appending(component: "\(self.c99name)\(suffix).build")
     }
 }

Sources/Build/BuildDescription/SwiftTargetBuildDescription.swift

@@ -66,7 +66,7 @@ public final class SwiftTargetBuildDescription {
     /// Path to the bundle generated for this module (if any).
     var bundlePath: AbsolutePath? {
         if let bundleName = target.underlying.potentialBundleName, needsResourceBundle {
-            let suffix = self.defaultBuildParameters.suffix(triple: self.target.buildTriple)
+            let suffix = self.defaultBuildParameters.suffix
             return self.defaultBuildParameters.bundlePath(named: bundleName + suffix)
         } else {
             return nil
@@ -113,7 +113,7 @@ public final class SwiftTargetBuildDescription {
     }
 
     var modulesPath: AbsolutePath {
-        let suffix = self.defaultBuildParameters.suffix(triple: self.target.buildTriple)
+        let suffix = self.defaultBuildParameters.suffix
         return self.defaultBuildParameters.buildPath.appending(component: "Modules\(suffix)")
     }
 

Sources/CoreCommands/SwiftCommandState.swift

@@ -725,7 +725,10 @@ public final class SwiftCommandState {
     when building on macOS.
     """
 
-    private func _buildParams(toolchain: UserToolchain) throws -> BuildParameters {
+    private func _buildParams(
+        toolchain: UserToolchain,
+        destination: BuildParameters.Destination
+    ) throws -> BuildParameters {
         let triple = toolchain.targetTriple
 
         let dataPath = self.scratchDirectory.appending(
@@ -737,6 +740,7 @@ public final class SwiftCommandState {
         }
 
         return try BuildParameters(
+            destination: destination,
             dataPath: dataPath,
             configuration: options.build.configuration,
             toolchain: toolchain,
@@ -796,7 +800,7 @@ public final class SwiftCommandState {
 
     private lazy var _toolsBuildParameters: Result<BuildParameters, Swift.Error> = {
         Result(catching: {
-            try _buildParams(toolchain: self.getHostToolchain())
+            try _buildParams(toolchain: self.getHostToolchain(), destination: .host)
         })
     }()
 
@@ -808,7 +812,7 @@ public final class SwiftCommandState {
 
     private lazy var _productsBuildParameters: Result<BuildParameters, Swift.Error> = {
         Result(catching: {
-            try _buildParams(toolchain: self.getTargetToolchain())
+            try _buildParams(toolchain: self.getTargetToolchain(), destination: .target)
         })
     }()
 

Sources/SPMBuildCore/BuildParameters/BuildParameters.swift

@@ -26,6 +26,18 @@ public struct BuildParameters: Encodable {
         case auto
     }
 
+    /// The destination for which code should be compiled for.
+    public enum Destination: Encodable {
+        /// The destination for which build tools are compiled.
+        case host
+
+        /// The destination for which end products are compiled.
+        case target
+    }
+
+    /// The destination these parameters are going to be used for.
+    public let destination: Destination
+
     /// The path to the data directory.
     public var dataPath: AbsolutePath
 
@@ -118,6 +130,7 @@ public struct BuildParameters: Encodable {
     public var testingParameters: Testing
 
     public init(
+        destination: Destination,
         dataPath: AbsolutePath,
         configuration: BuildConfiguration,
         toolchain: Toolchain,
@@ -144,6 +157,7 @@ public struct BuildParameters: Encodable {
             omitFramePointers: nil
         )
 
+        self.destination = destination
         self.dataPath = dataPath
         self.configuration = configuration
         self._toolchain = _Toolchain(toolchain: toolchain)
@@ -243,18 +257,18 @@ public struct BuildParameters: Encodable {
 
     /// Returns the path to the dynamic library of a product for the current build parameters.
     func potentialDynamicLibraryPath(for product: ResolvedProduct) throws -> RelativePath {
-        try RelativePath(validating: "\(self.triple.dynamicLibraryPrefix)\(product.name)\(self.suffix(triple: product.buildTriple))\(self.triple.dynamicLibraryExtension)")
+        try RelativePath(validating: "\(self.triple.dynamicLibraryPrefix)\(product.name)\(self.suffix)\(self.triple.dynamicLibraryExtension)")
     }
 
     /// Returns the path to the binary of a product for the current build parameters, relative to the build directory.
     public func binaryRelativePath(for product: ResolvedProduct) throws -> RelativePath {
-        let potentialExecutablePath = try RelativePath(validating: "\(product.name)\(self.suffix(triple: product.buildTriple))\(self.triple.executableExtension)")
+        let potentialExecutablePath = try RelativePath(validating: "\(product.name)\(self.suffix)\(self.triple.executableExtension)")
 
         switch product.type {
         case .executable, .snippet:
             return potentialExecutablePath
         case .library(.static):
-            return try RelativePath(validating: "lib\(product.name)\(self.suffix(triple: product.buildTriple))\(self.triple.staticLibraryExtension)")
+            return try RelativePath(validating: "lib\(product.name)\(self.suffix)\(self.triple.staticLibraryExtension)")
         case .library(.dynamic):
             return try potentialDynamicLibraryPath(for: product)
         case .library(.automatic), .plugin:
@@ -333,7 +347,7 @@ extension Triple {
 extension BuildParameters {
     /// Suffix appended to build manifest nodes to distinguish nodes created for tools from nodes created for
     /// end products, i.e. nodes for host vs target triples.
-    package func suffix(triple: BuildTriple) -> String {
-        if triple == .tools { "-tool" } else { "" }
+    package var suffix: String {
+        if destination == .host { "-tool" } else { "" }
     }
 }

Sources/swift-bootstrap/main.swift

@@ -282,6 +282,7 @@ struct SwiftBootstrapBuildTool: ParsableCommand {
             )
 
             let buildParameters = try BuildParameters(
+                destination: .target,
                 dataPath: dataPath,
                 configuration: configuration,
                 toolchain: self.targetToolchain,