Index: clang/lib/Driver/Driver.cpp
===================================================================
--- clang/lib/Driver/Driver.cpp
+++ clang/lib/Driver/Driver.cpp
@@ -5970,9 +5970,16 @@
   Names.emplace_back(Tool);
 }
 
-static bool ScanDirForExecutable(SmallString<128> &Dir, StringRef Name) {
+static bool canExecute(llvm::vfs::FileSystem &VFS, StringRef Path) {
+  auto Status = VFS.status(Path);
+  return Status &&
+         (Status->getPermissions() & llvm::sys::fs::perms::all_exe) != 0;
+}
+
+static bool ScanDirForExecutable(llvm::vfs::FileSystem &VFS,
+                                 SmallString<128> &Dir, StringRef Name) {
   llvm::sys::path::append(Dir, Name);
-  if (llvm::sys::fs::can_execute(Twine(Dir)))
+  if (canExecute(VFS, Dir))
     return true;
   llvm::sys::path::remove_filename(Dir);
   return false;
@@ -5985,13 +5992,14 @@
   // Respect a limited subset of the '-Bprefix' functionality in GCC by
   // attempting to use this prefix when looking for program paths.
   for (const auto &PrefixDir : PrefixDirs) {
-    if (llvm::sys::fs::is_directory(PrefixDir)) {
+    auto Status = getVFS().status(PrefixDir);
+    if (Status && Status->isDirectory()) {
       SmallString<128> P(PrefixDir);
-      if (ScanDirForExecutable(P, Name))
+      if (ScanDirForExecutable(getVFS(), P, Name))
         return std::string(P.str());
     } else {
       SmallString<128> P((PrefixDir + Name).str());
-      if (llvm::sys::fs::can_execute(Twine(P)))
+      if (canExecute(getVFS(), P))
         return std::string(P.str());
     }
   }
@@ -6007,7 +6015,7 @@
     // of gcc in the program path
     for (const auto &Path : List) {
       SmallString<128> P(Path);
-      if (ScanDirForExecutable(P, TargetSpecificExecutable))
+      if (ScanDirForExecutable(getVFS(), P, TargetSpecificExecutable))
         return std::string(P.str());
     }