build: define build path structure in BuildSystemProvider.Kind

There are a few places that check the BuildSystemProvider.Kind is Xcode
to determine the build directory structure.  With the upcoming Swift
Build integration, which uses the "Xcode path" structure, we would need
to update all instances to check the two build system provider kinds.

Add an extension on the BuildSystemProvider.Kind that create a boolean
variable `useXcodeBuildEngine`, which determines whether the build
system should use the xcode path structure or not.  In addition, update
the code that requires a  "isXcodeBuildSystemEnabled" to return this
build system provider variable.

This will hopefully help address swiftlang#8272 when swiftlang#8271, where it adds
`case .swiftbuild: return true` to the `useXcodeBuildEngine`

Sources/CoreCommands/SwiftCommandState.swift

@@ -441,7 +441,7 @@ public final class SwiftCommandState {
             self.observabilityHandler.progress,
             self.observabilityHandler.prompt
         )
-        let isXcodeBuildSystemEnabled = self.options.build.buildSystem == .xcode
+        let isXcodeBuildSystemEnabled = self.options.build.buildSystem.useXcodeBuildEngine
         let workspace = try Workspace(
             fileSystem: self.fileSystem,
             location: .init(
@@ -459,7 +459,7 @@ public final class SwiftCommandState {
             configuration: .init(
                 skipDependenciesUpdates: options.resolver.skipDependencyUpdate,
                 prefetchBasedOnResolvedFile: options.resolver.shouldEnableResolverPrefetching,
-                shouldCreateMultipleTestProducts: toolWorkspaceConfiguration.wantsMultipleTestProducts || options.build.buildSystem == .xcode,
+                shouldCreateMultipleTestProducts: toolWorkspaceConfiguration.wantsMultipleTestProducts || options.build.buildSystem.useXcodeBuildEngine,
                 createREPLProduct: toolWorkspaceConfiguration.wantsREPLProduct,
                 additionalFileRules: isXcodeBuildSystemEnabled ? FileRuleDescription.xcbuildFileTypes : FileRuleDescription.swiftpmFileTypes,
                 sharedDependenciesCacheEnabled: self.options.caching.useDependenciesCache,
@@ -795,7 +795,7 @@ public final class SwiftCommandState {
             workers: options.build.jobs ?? UInt32(ProcessInfo.processInfo.activeProcessorCount),
             sanitizers: options.build.enabledSanitizers,
             indexStoreMode: options.build.indexStoreMode.buildParameter,
-            isXcodeBuildSystemEnabled: options.build.buildSystem == .xcode,
+            isXcodeBuildSystemEnabled: options.build.buildSystem.useXcodeBuildEngine,
             prepareForIndexing: prepareForIndexingMode,
             debuggingParameters: .init(
                 debugInfoFormat: options.build.debugInfoFormat.buildParameter,

Sources/SPMBuildCore/BuildSystem/BuildSystem.swift

@@ -168,6 +168,14 @@ public struct BuildSystemProvider {
     }
 }
 
+extension BuildSystemProvider.Kind {
+    public var useXcodeBuildEngine: Bool {
+        switch self {
+            case .native: return false
+            case .xcode: return true
+        }
+    }
+}
 private enum Errors: Swift.Error {
     case buildSystemProviderNotRegistered(kind: BuildSystemProvider.Kind)
 }

Sources/SPMBuildCore/Triple+Extensions.swift

@@ -27,6 +27,6 @@ extension Triple {
         // Use "apple" as the subdirectory because in theory Xcode build system
         // can be used to build for any Apple platform and it has its own
         // conventions for build subpaths based on platforms.
-        buildSystem == .xcode ? "apple" : self.platformBuildPathComponent
+        buildSystem.useXcodeBuildEngine ? "apple" : self.platformBuildPathComponent
     }
 }

Sources/swift-bootstrap/main.swift

@@ -289,7 +289,7 @@ struct SwiftBootstrapBuildTool: AsyncParsableCommand {
                 triple: self.hostToolchain.targetTriple,
                 flags: buildFlags,
                 architectures: architectures,
-                isXcodeBuildSystemEnabled: buildSystem == .xcode,
+                isXcodeBuildSystemEnabled: buildSystem.useXcodeBuildEngine,
                 driverParameters: .init(
                     explicitTargetDependencyImportCheckingMode: explicitTargetDependencyImportCheck == .error ? .error : .none,
                     useIntegratedSwiftDriver: useIntegratedSwiftDriver,