[BuildPlan] Make build descriptions identifiable just like Resolved{Product, Module}

Author: xedin

Sources/Build/BuildDescription/ClangModuleBuildDescription.swift

@@ -42,6 +42,11 @@ public final class ClangModuleBuildDescription {
     /// The build parameters.
     let buildParameters: BuildParameters
 
+    /// The destination for while this module is built.
+    public var destination: BuildParameters.Destination {
+        self.buildParameters.destination
+    }
+
     /// The build environment.
     var buildEnvironment: BuildEnvironment {
         buildParameters.buildEnvironment

Sources/Build/BuildDescription/ModuleBuildDescription.swift

@@ -121,6 +121,15 @@ public enum ModuleBuildDescription: SPMBuildCore.ModuleBuildDescription {
         }
     }
 
+    var destination: BuildParameters.Destination {
+        switch self {
+        case .swift(let buildDescription):
+            buildDescription.destination
+        case .clang(let buildDescription):
+            buildDescription.destination
+        }
+    }
+
     var toolsVersion: ToolsVersion {
         switch self {
         case .swift(let buildDescription):
@@ -139,3 +148,14 @@ public enum ModuleBuildDescription: SPMBuildCore.ModuleBuildDescription {
         }
     }
 }
+
+extension ModuleBuildDescription: Identifiable {
+    public struct ID: Hashable {
+        let moduleID: ResolvedModule.ID
+        let destination: BuildParameters.Destination
+    }
+
+    public var id: ID {
+        ID(moduleID: self.module.id, destination: self.destination)
+    }
+}

Sources/Build/BuildDescription/ProductBuildDescription.swift

@@ -37,6 +37,11 @@ public final class ProductBuildDescription: SPMBuildCore.ProductBuildDescription
     /// The build parameters.
     public let buildParameters: BuildParameters
 
+    /// The destination for while this product is built.
+    public var destination: BuildParameters.Destination {
+        self.buildParameters.destination
+    }
+
     /// All object files to link into this product.
     ///
     // Computed during build planning.
@@ -397,6 +402,17 @@ public final class ProductBuildDescription: SPMBuildCore.ProductBuildDescription
     }
 }
 
+extension ProductBuildDescription: Identifiable {
+    public struct ID: Hashable {
+        let productID: ResolvedProduct.ID
+        let destination: BuildParameters.Destination
+    }
+
+    public var id: ID {
+        ID(productID: self.product.id, destination: self.destination)
+    }
+}
+
 extension SortedArray where Element == AbsolutePath {
     public static func +=<S: Sequence>(lhs: inout SortedArray, rhs: S) where S.Iterator.Element == AbsolutePath {
         lhs.insert(contentsOf: rhs)

Sources/Build/BuildDescription/SwiftModuleBuildDescription.swift

@@ -49,6 +49,11 @@ public final class SwiftModuleBuildDescription {
     /// The build parameters for this target.
     let buildParameters: BuildParameters
 
+    /// The destination for while this module is built.
+    public var destination: BuildParameters.Destination {
+        self.buildParameters.destination
+    }
+
     /// The build parameters for the macro dependencies of this target.
     let macroBuildParameters: BuildParameters