Added builddir option to clang-tidy to point to json folder (#688)

Detect compille_commands.json files for clang-tidy

autoload/ale/c.vim

@@ -0,0 +1,24 @@
+" Author: gagbo <gagbobada@gmail.com>
+" Description: Functions for integrating with C-family linters.
+
+
+let g:ale_c_build_dir_names = get(g:, 'ale_c_build_dir_names', [
+\   'build',
+\   'bin',
+\])
+
+" Given a buffer number, find the build subdirectory with compile commands
+" The subdirectory is returned without the trailing /
+function! ale#c#FindCompileCommands(buffer) abort
+    for l:path in ale#path#Upwards(expand('#' . a:buffer . ':p:h'))
+        for l:dirname in ale#Var(a:buffer, 'c_build_dir_names')
+            let l:c_build_dir = l:path . '/' . l:dirname
+
+            if filereadable(l:c_build_dir . '/compile_commands.json')
+                return l:c_build_dir
+            endif
+        endfor
+    endfor
+
+    return ''
+endfunction