[Xcodeproj] Create symlink'ed dylibs for C frameworks

This patch adds library search path to generated Xcode projects to a directory with symlinks to C framework binaries so that client provided modulemap can work with Xcode as well as SwiftPM. - https://bugs.swift.org/browse/SR-2465 - <rdar://problem/28038845> SR-2465: Xcode project cannot use C language target with custom module map

Author: aciidgh

Sources/Xcodeproj/Module+PBXProj.swift

@@ -52,6 +52,7 @@ extension Module {
  var releaseConfigurationReference: String { return "_ReleaseConf_\(c99name)" }
  var compilePhaseReference: String { return "CompilePhase_\(c99name)" }
  var linkPhaseReference: String { return "___LinkPhase_\(c99name)" }
+ var shellScriptPhaseReference: String { return "_ScriptPhase_\(c99name)" }
 }
 
 func fileRef(forLinkPhaseChild module: Module, from: Module) -> String {
@@ -218,6 +219,12 @@ extension Module {
  var buildSettings = [String: Any]()
  let plistPath = xcodeProjectPath.appending(component: infoPlistFileName)
 
+ // Add default library search path to the directory where symlinks to framework
+ // binaries will be put with name `lib<library-name>.dylib` so that autolinking
+ // can proceed without providing another modulemap for Xcode projects.
+ // See: https://bugs.swift.org/browse/SR-2465
+ buildSettings["LIBRARY_SEARCH_PATHS"] = ["$(PROJECT_TEMP_DIR)/SymlinkLibs/"]
+
  if isTest {
  buildSettings["EMBEDDED_CONTENT_CONTAINS_SWIFT"] = "YES"
 

Sources/Xcodeproj/pbxproj().swift

@@ -179,7 +179,14 @@ public func pbxproj(srcroot: AbsolutePath, projectRoot: AbsolutePath, xcodeprojP
  print(" \(module.targetReference) = {")
  print(" isa = PBXNativeTarget;")
  print(" buildConfigurationList = \(module.configurationListReference);")
- print(" buildPhases = (\(module.compilePhaseReference), \(module.linkPhaseReference));")
+
+ print(" buildPhases = (")
+ // Add a shell script phase for clang module libraries for SR-2465.
+ if module.isClangModuleLibrary {
+ print("\(module.shellScriptPhaseReference), ")
+ }
+ print("\(module.compilePhaseReference), \(module.linkPhaseReference));")
+
  print(" buildRules = ();")
  print(" dependencies = (\(module.nativeTargetDependencies));")
  print(" name = '\(module.name)';")
@@ -196,6 +203,16 @@ public func pbxproj(srcroot: AbsolutePath, projectRoot: AbsolutePath, xcodeprojP
  print(" sourceTree = BUILT_PRODUCTS_DIR;")
  print(" };")
 
+ // shell script build phase.
+ if module.isClangModuleLibrary {
+ print(" \(module.shellScriptPhaseReference) = {")
+ print(" isa = PBXShellScriptBuildPhase;")
+ print(" shellPath = /bin/sh;")
+ print(" shellScript = \"mkdir -p \\\"$PROJECT_TEMP_DIR/SymlinkLibs\\\"\nln -sf \\\"$BUILT_PRODUCTS_DIR/$EXECUTABLE_PATH\\\" \\\"$PROJECT_TEMP_DIR/SymlinkLibs/lib$EXECUTABLE_NAME.dylib\\\"\";")
+ print(" runOnlyForDeploymentPostprocessing = 0;")
+ print(" };")
+ }
+
  // sources build phase
  print(" \(module.compilePhaseReference) = {")
  print(" isa = PBXSourcesBuildPhase;")
@@ -474,6 +491,14 @@ private extension SupportedLanguageExtension {
 }
 
 private extension Module {
+
+ var isClangModuleLibrary: Bool {
+ if case let clangModule as ClangModule = self, clangModule.type == .library {
+ return true
+ }
+ return false
+ }
+
  func fileType(forSource source: RelativePath) -> String {
  switch self {
  case is SwiftModule: