[HeaderSearch] loadSubdirectoryModuleMaps should respect -working-directory

[arphaman]

Summary

Include search paths can be relative paths. The loadSubdirectoryModuleMaps function should account for that and respect the -working-directory parameter given to Clang.

[bruno]

LGTM

lib/Lex/HeaderSearch.cpp

 void HeaderSearch::loadSubdirectoryModuleMaps(DirectoryLookup &SearchDir) {
   assert(HSOpts->ImplicitModuleMaps &&
          "Should not be loading subdirectory module maps");
 
   if (SearchDir.haveSearchedAllModuleMaps())
     return;
 
   std::error_code EC;
+  SmallString<128> Dir = SearchDir.getDir()->getName();
+  FileMgr.makeAbsolutePath(Dir);
   SmallString<128> DirNative;
-  llvm::sys::path::native(SearchDir.getDir()->getName(), DirNative);
+  llvm::sys::path::native(Dir, DirNative);
   llvm::vfs::FileSystem &FS = *FileMgr.getVirtualFileSystem();
   for (llvm::vfs::directory_iterator Dir = FS.dir_begin(DirNative, EC), DirEnd;
        Dir != DirEnd && !EC; Dir.increment(EC)) {
     bool IsFramework = llvm::sys::path::extension(Dir->path()) == ".framework";
     if (IsFramework == SearchDir.isFramework())
       loadModuleMapFile(Dir->path(), SearchDir.isSystemHeaderDirectory(),
                         SearchDir.isFramework());
   }

test/Modules/Inputs/subdirectory-module-maps-working-dir/subdir_module/h1.h

+int bar();

test/Modules/Inputs/subdirectory-module-maps-working-dir/subdir_module/module.map

+module ModuleInSubdir {
+header "h1.h"
+  export *
+}
+

test/Modules/subdirectory-module-maps-working-dir.m

+// RUN: rm -rf %t
+// RUN: %clang -fsyntax-only -fmodules -fmodules-cache-path=%t \
+// RUN:    -working-directory %S/Inputs \
+// RUN:    -I subdirectory-module-maps-working-dir \
+// RUN:    %s -Werror=implicit-function-declaration -Xclang -verify
+
+@import ModuleInSubdir;
+
+void foo() {
+  int x = bar();
+}
+
+// expected-no-diagnostics