[clangd] Don't mangle workdir-relevant driver path in compile commands

Summary:
We can't resolve this (if it's a symlink) without further refactoring, but the
current behaviour is just incorrect.

Reviewers: kadircet

Subscribers: ilya-biryukov, MaskRay, jkorous, arphaman, usaxena95, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D82011

clang-tools-extra/clangd/CompileCommands.cpp

@@ -135,6 +135,12 @@ static std::string resolveDriver(llvm::StringRef Driver, bool FollowSymlink,
   // First, eliminate relative paths.
   std::string Storage;
   if (!llvm::sys::path::is_absolute(Driver)) {
+    // If it's working-dir relative like bin/clang, we can't resolve it.
+    // FIXME: we could if we had the working directory here.
+    // Let's hope it's not a symlink.
+    if (llvm::any_of(Driver,
+                     [](char C) { return llvm::sys::path::is_separator(C); }))
+      return Driver.str();
     // If the driver is a generic like "g++" with no path, add clang dir.
     if (ClangPath &&
         (Driver == "clang" || Driver == "clang++" || Driver == "gcc" ||

clang-tools-extra/clangd/unittests/CompileCommandsTests.cpp

@@ -115,7 +115,7 @@ TEST(CommandMangler, ClangPath) {
 
   Cmd = {"foo/unknown-binary", "foo.cc"};
   Mangler.adjust(Cmd);
-  EXPECT_EQ(testPath("fake/unknown-binary"), Cmd.front());
+  EXPECT_EQ("foo/unknown-binary", Cmd.front());
 }
 
 // Only run the PATH/symlink resolving test on unix, we need to fiddle