Refactor running of local Node programs with a helper function

ale_linters/javascript/flow.vim

@@ -1,22 +1,13 @@
 " Author: Zach Perrault -- @zperrault
 " Description: FlowType checking for JavaScript files
 
-let g:ale_javascript_flow_executable =
-\   get(g:, 'ale_javascript_flow_executable', 'flow')
-
-let g:ale_javascript_flow_use_global =
-\   get(g:, 'ale_javascript_flow_use_global', 0)
+call ale#Set('javascript_flow_executable', 'flow')
+call ale#Set('javascript_flow_use_global', 0)
 
 function! ale_linters#javascript#flow#GetExecutable(buffer) abort
-    if ale#Var(a:buffer, 'javascript_flow_use_global')
-        return ale#Var(a:buffer, 'javascript_flow_executable')
-    endif
-
-    return ale#path#ResolveLocalPath(
-    \   a:buffer,
+    return ale#node#FindExecutable(a:buffer, 'javascript_flow', [
     \   'node_modules/.bin/flow',
-    \   ale#Var(a:buffer, 'javascript_flow_executable')
-    \)
+    \])
 endfunction
 
 function! ale_linters#javascript#flow#GetCommand(buffer) abort