Added tests for clangd compile commands dectection

ale_linters/c/clangd.vim

@@ -3,6 +3,7 @@
 
 call ale#Set('c_clangd_executable', 'clangd')
 call ale#Set('c_clangd_options', '')
+call ale#Set('c_build_dir', '')
 
 function! ale_linters#c#clangd#GetCommand(buffer) abort
     let l:build_dir = ale#c#GetBuildDirectory(a:buffer)

ale_linters/cpp/clangd.vim

@@ -3,6 +3,7 @@
 
 call ale#Set('cpp_clangd_executable', 'clangd')
 call ale#Set('cpp_clangd_options', '')
+call ale#Set('c_build_dir', '')
 
 function! ale_linters#cpp#clangd#GetCommand(buffer) abort
     let l:build_dir = ale#c#GetBuildDirectory(a:buffer)

test/command_callback/test_c_clangd_command_callbacks.vader

@@ -18,9 +18,9 @@ Execute(The project root should be detected correctly):
 
   AssertLSPProject ''
 
-  call ale#test#SetFilename('clangd_paths/dummy.c')
+  call ale#test#SetFilename('clangd_paths/with_compile_commands/dummy.c')
 
-  AssertLSPProject ale#path#Simplify(g:dir . '/clangd_paths')
+  AssertLSPProject ale#path#Simplify(g:dir . '/clangd_paths/with_compile_commands')
 
 Execute(The executable should be configurable):
   let g:ale_c_clangd_executable = 'foobar'
@@ -32,3 +32,15 @@ Execute(The options should be configurable):
 
   AssertLinter 'clangd', ale#Escape('clangd') . ' ' . b:ale_c_clangd_options
 
+Execute(The compile command database should be detected correctly):
+  call ale#test#SetFilename('clangd_paths/with_build_dir/dummy_src/dummy.c')
+
+  let b:ale_c_clangd_options = ''
+  let b:ale_c_build_dir = ''
+  let b:ale_c_build_dir_names = ['unusual_build_dir_name']
+  let b:ale_c_parse_compile_commands = 1
+
+  AssertLinter 'clangd', ale#Escape('clangd')
+  \  . ' -compile-commands-dir='
+  \  . ale#Escape(g:dir . '/clangd_paths/with_build_dir/unusual_build_dir_name')
+