ccls: Wrong diagnostics on macOS w/ clang10

Observed behavior

• compile_commands.json

[
  {
    "directory": "/Users/flanggut/tmp/ccls",
    "file": "/Users/flanggut/tmp/ccls/main.cpp",
    "arguments": [
      "/usr/local/opt/llvm/bin/clang++",
      "-std=c++17",
      "-isystem /Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/include",
      "-isystem /Library/Developer/CommandLineTools/usr/lib/clang/11.0.3/include/",
      "-I.",
      "main.cpp"
    ]
  }
]

• main.cpp

#include <chrono>
auto clk() {
  return std::chrono::high_resolution_clock::now();
}
int main(int /*argc*/, char** /*argv*/) {
  auto clk0 = clk();
}

ccls --index=. -v=2 Correctly identifies and and indexes all headers.

/usr/local/opt/llvm/bin/clang++ --driver-mode=g++ -std=c++17 -isystem /Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/include -isystem /Library/Developer/CommandLineTools/usr/lib/clang/11.0.3/include/ -I. main.cpp

File compiles without issues.

In my editor ccls claims that <chrono> include cannot be found under ./chrono, note that the error is always shown for the include path -I., if I change that to -I.. the error will show that ../chrono cannot be found.

This only happens since clang/llvm10 and does not happen if I compile ccls against clang/llvm9.

Expected behavior

No diagnostics should be shown in an editor.

Steps to reproduce

1. brew install ccls (recently updated to use llvm10)
2. Open file in editor w/ ccls as language server

System information

• ccls version (git describe --tags --long): brew info ccls
• clang version: clang version 10.0.0
• OS: x86_64-apple-darwin19.4.0
• Editor: nvim / vscode
• Language client (and version): coc.nvim / vscode-ccls