Allow a custom env for more xcrun invocations

Basically a continuation of #1766

Author: neonichu

Sources/Build/Toolchain.swift

@@ -16,7 +16,7 @@ public protocol Toolchain {
     var swiftCompiler: AbsolutePath { get }
 
     /// Path of the `clang` compiler.
-    func getClangCompiler() throws -> AbsolutePath
+    func getClangCompiler(environment: [String:String]) throws -> AbsolutePath
 
     /// Additional flags to be passed to the C compiler.
     var extraCCFlags: [String] { get }
@@ -30,3 +30,9 @@ public protocol Toolchain {
     /// The dynamic library extension, for e.g. dylib, so.
     var dynamicLibraryExtension: String { get }
 }
+
+extension Toolchain {
+    func getClangCompiler() throws -> AbsolutePath {
+        return try getClangCompiler(environment: Process.env)
+    }
+}

Sources/Build/llbuild.swift

@@ -87,7 +87,7 @@ public struct LLBuildManifestGenerator {
     }
 
     /// Generate manifest at the given path.
-    public func generateManifest(at path: AbsolutePath) throws {
+    public func generateManifest(at path: AbsolutePath, environment: [String:String] = Process.env) throws {
         var targets = Targets()
 
         // Create commands for all target description in the plan.
@@ -99,7 +99,7 @@ public struct LLBuildManifestGenerator {
                     buildByDefault: plan.graph.reachableTargets.contains(target),
                     isTest: description.isTestTarget)
             case .clang(let description):
-                targets.append(try createClangCompileTarget(description),
+                targets.append(try createClangCompileTarget(description, environment: environment),
                     buildByDefault: plan.graph.reachableTargets.contains(target),
                     isTest: description.isTestTarget)
             }
@@ -215,7 +215,7 @@ public struct LLBuildManifestGenerator {
     }
 
     /// Create a llbuild target for a Clang target description.
-    private func createClangCompileTarget(_ target: ClangTargetBuildDescription) throws -> Target {
+    private func createClangCompileTarget(_ target: ClangTargetBuildDescription, environment: [String:String] = Process.env) throws -> Target {
 
         let standards = [
             (target.clangTarget.cxxLanguageStandard, SupportedLanguageExtension.cppExtensions),
@@ -241,7 +241,7 @@ public struct LLBuildManifestGenerator {
                 //FIXME: Should we add build time dependency on dependent targets?
                 inputs: [path.source.asString],
                 outputs: [path.object.asString],
-                args: [try plan.buildParameters.toolchain.getClangCompiler().asString] + args,
+                args: [try plan.buildParameters.toolchain.getClangCompiler(environment: environment).asString] + args,
                 deps: path.deps.asString)
             return Command(name: path.object.asString, tool: clang)
         })

Sources/Workspace/UserToolchain.swift

@@ -129,7 +129,7 @@ public final class UserToolchain: Toolchain {
         return lookupExecutablePath(filename: getenv(variable), searchPaths: searchPaths)
     }
 
-    public func getClangCompiler() throws -> AbsolutePath {
+    public func getClangCompiler(environment: [String:String]) throws -> AbsolutePath {
 
         if let clangCompiler = _clangCompiler {
             return clangCompiler
@@ -142,7 +142,7 @@ public final class UserToolchain: Toolchain {
             clangCompiler = value
         } else {
             // No value in env, so search for `clang`.
-            let foundPath = try Process.checkNonZeroExit(arguments: whichClangArgs).chomp()
+            let foundPath = try Process.checkNonZeroExit(arguments: whichClangArgs, environment: environment).chomp()
             guard !foundPath.isEmpty else {
                 throw InvalidToolchainDiagnostic("could not find `clang`")
             }

Tests/BuildTests/BuildPlanTests.swift

@@ -31,7 +31,7 @@ private struct MockToolchain: Toolchain {
   #else
     let dynamicLibraryExtension = "so"
   #endif
-    func getClangCompiler() throws -> AbsolutePath {
+    func getClangCompiler(environment: [String:String]) throws -> AbsolutePath {
         return AbsolutePath("/fake/path/to/clang")
     }
 }