Arch Linux

Description:

The ccls package has the wrong clang resource dir hardcoded after a clang update.
While this doesn't crash ccls, it causes it to give wrong diagnostic messages.

Additional info:
* package version(s): ccls 0.20190823.6-1 (possibly others)

The resource dir is hardcoded into the executable at compile time: https://github.com/MaskRay/ccls/wiki/Customization#clangresourcedir

This means that everytime the output of `clang -print-resource-dir` changes (i.e. after every clang upstream release), ccls needs to be recompiled.

Steps to reproduce:

Try creating a variable of type `std::string` while including both `<string>` and `<memory>` and it will give you the following diagnostics error:

```
main.cpp:5:17 Error [ccls 2] cannot initialize a variable of type 'std::string' (aka 'int') with an lvalue of type 'const char [12]'
```

I have attached the corresponding main.cpp and .ccls file (the .ccls file is empty, but it has to exist in the same folder as `main.cpp`).


One can also detect that the resource dir is wrong by running `ccls --index=.` in a cpp project. It will produce a line like this:

```
16:56:04 ccls initialize.cc:314 I use -resource-dir=/usr/lib/clang/10.0.0
```

If the `resource-dir` doesn't match the output of `clang -print-resource-dir`, you may get the problems described above.