Generate the compilation database through CMake

Use an Emacs directory-local variable to specify to ccls where the compilation
directory lives, tell CMake to generate the compilation database, and remove
bear from the environment.

Add clang to the environment for clang-format.

.dir-locals.el

@@ -0,0 +1,4 @@
+;;; Directory Local Variables
+;;; For more information see (info "(emacs) Directory Variables")
+
+((c-mode . ((ccls-args . '("--init={\"compilationDatabaseDirectory\": \"clox/_build\"}")))))

clox/CMakeLists.txt

@@ -2,4 +2,6 @@ cmake_minimum_required(VERSION 2.19)
 
 project(Lox C)
 
+set(CMAKE_EXPORT_COMPILE_COMMANDS ON)
+
 add_subdirectory(src)

environment.scm

@@ -9,4 +9,5 @@
        (specification->package "dejagnu")
        (specification->package "gcc-toolchain")
        (specification->package "ccls")
-       (specification->package "bear")))
+       ;; For clang-format
+       (specification->package "clang")))