Add support for parsing compile_commands.json files for C compilers

doc/ale-c.txt

@@ -25,13 +25,28 @@ g:ale_c_build_dir                                           *g:ale_c_build_dir*
   Type: |String|
   Default: `''`
 
-  A path to the directory containing the `compile_commands.json` file to use
-  with c-family linters. Usually setting this option to a non-empty string
-  will override the |g:ale_c_build_dir_names| option to impose a compilation
-  database (it can be useful if multiple builds are in multiple build
-  subdirectories in the project tree).
-  This feature is also most useful for the clang tools linters, wrapped
-  around LibTooling (namely clang-tidy here)
+  For programs that can read `compile_commands.json` files, this option can be
+  set to the directory containing the file for the project. ALE will try to
+  determine the location of `compile_commands.json` automatically, but if your
+  file exists in some other directory, you can set this option so ALE will
+  know where it is.
+
+  This directory will be searched instead of |g:ale_c_build_dir_names|.
+
+
+g:ale_c_parse_compile_commands                 *g:ale_c_parse_compile_commands*
+                                               *b:ale_c_parse_compile_commands*
+  Type: |Number|
+  Default: `0`
+
+  If set to `1`, ALE will parse `compile_commands.json` files to automatically
+  determine flags for C or C++ compilers. ALE will first search for the
+  nearest `compile_commands.json` file, and then look for
+  `compile_commands.json` files in the directories for
+  |g:ale_c_build_dir_names|.
+
+  If |g:ale_c_parse_makefile| or |b:ale_c_parse_makefile| is set to `1`, the
+  output of `make -n` will be preferred over `compile_commands.json` files.
 
 
 g:ale_c_parse_makefile                                 *g:ale_c_parse_makefile*

doc/ale-cpp.txt

@@ -10,6 +10,7 @@ The following C options also apply to some C++ linters too.
 * |g:ale_c_build_dir_names|
 * |g:ale_c_build_dir|
 * |g:ale_c_parse_makefile|
+* |g:ale_c_parse_compile_commands|
 
 
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