feat(erlang/erlc): add option for custom executable

test/command_callback/test_erlang_erlc_command_callback.vader

@@ -0,0 +1,40 @@
+Before:
+  call ale#assert#SetUpLinterTest('erlang', 'erlc')
+
+After:
+  call ale#assert#TearDownLinterTest()
+
+Execute(The default command should be correct.):
+    let g:cmd = ale_linters#erlang#erlc#GetCommand(bufnr(''))
+    let g:regex = '^''erlc''\s\+-o\s\+[^\s]\+\s\+%t'
+    let g:matched = match(g:cmd, g:regex)
+
+    " match returns -1 if not found
+    AssertNotEqual
+    \   g:matched,
+    \   -1,
+    \   'Command error: expected [' . g:cmd . '] to match [' . g:regex . ']'
+
+Execute(The command should accept configured executable.):
+    let b:ale_erlang_erlc_executable = '/usr/bin/erlc'
+    let g:cmd = ale_linters#erlang#erlc#GetCommand(bufnr(''))
+    let g:regex = '^''/usr/bin/erlc''\s\+-o\s\+[^\s]\+\s\+%t'
+    let g:matched = match(g:cmd, g:regex)
+
+    " match returns -1 if not found
+    AssertNotEqual
+    \   g:matched,
+    \   -1,
+    \   'Command error: expected [' . g:cmd . '] to match [' . g:regex . ']'
+
+Execute(The command should accept configured options.):
+    let b:ale_erlang_erlc_options = '-I include'
+    let g:cmd = ale_linters#erlang#erlc#GetCommand(bufnr(''))
+    let g:regex = '^''erlc''\s\+-o\s\+[^\s]\+\s\+-I include\s\+%t'
+    let g:matched = match(g:cmd, g:regex)
+
+    " match returns -1 if not found
+    AssertNotEqual
+    \   g:matched,
+    \   -1,
+    \   'Command error: expected [' . g:cmd . '] to match [' . g:regex . ']'