Cannot build

Cloned the repo, ran `make install`, got the following error back:
```
~/skhd $ make install
rm -rf ./bin
mkdir -p ./bin
clang src/skhd.c -std=c99 -Wall -O2 -framework Cocoa -framework Carbon -framework CoreServices -o bin/skhd
In file included from src/skhd.c:30:
src/service.h:136:9: error: call to undeclared function '_NSGetExecutablePath'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration]
136 | if (_NSGetExecutablePath(exe_path, &exe_path_size) < 0) {
| ^
```
The readme says building requires "xcode-8 command-line tools". Does that mean `>= 8` or `== 8`?

If `== 8`, how does one even downgrade their Xcode command-line tools version?

According to `pkgutil --pkg-info=com.apple.pkg.CLTools_Executables`, I'm on version 15.

Start with the `make install` command in the repository and inspect the `_NSGetExecutablePath` call in `src/service.h`, as well as the inclusion context in `src/skhd.c`. Check the README's Xcode command-line-tools requirement against the reported version 15 environment. Done means the documented build works or the supported tool version and required change are clearly established.

Written by the indexing model from the issue text.