Add llc integration for LLVM IR (#979)

Check LLVM IR with llc

test/command_callback/test_llc_command_callback.vader

@@ -0,0 +1,39 @@
+Before:
+  Save g:ale_llvm_llc_executable
+
+  unlet! g:ale_llvm_llc_executable
+  unlet! b:ale_llvm_llc_executable
+
+  runtime ale_linters/llvm/llc.vim
+
+  function! AssertHasPrefix(str, prefix) abort
+    let msg = printf("'%s' is expected to be prefixed with '%s'", a:str, a:prefix)
+    AssertEqual stridx(a:str, a:prefix), 0, msg
+  endfunction
+
+After:
+  unlet! g:ale_llvm_llc_executable
+  unlet! b:ale_llvm_llc_executable
+  delfunction AssertHasPrefix
+  Restore
+
+Execute(llc command is customizable):
+  let cmd = ale_linters#llvm#llc#GetCommand(bufnr(''))
+  call AssertHasPrefix(cmd, ale#Escape('llc'))
+
+  let g:ale_llvm_llc_executable = 'llc-5.0'
+  let cmd = ale_linters#llvm#llc#GetCommand(bufnr(''))
+  call AssertHasPrefix(cmd, ale#Escape('llc-5.0'))
+
+  let b:ale_llvm_llc_executable = 'llc-4.0'
+  let cmd = ale_linters#llvm#llc#GetCommand(bufnr(''))
+  call AssertHasPrefix(cmd, ale#Escape('llc-4.0'))
+
+Execute(GetCommand() escapes the returned path):
+  let b:ale_llvm_llc_executable = '/path/space contained/llc'
+  let cmd = ale_linters#llvm#llc#GetCommand(bufnr(''))
+  call AssertHasPrefix(cmd, ale#Escape('/path/space contained/llc'))
+
+Execute(GetExecutable() does not escape the returned path):
+  let b:ale_llvm_llc_executable = '/path/space contained/llc'
+  AssertEqual ale_linters#llvm#llc#GetExecutable(bufnr('')), '/path/space contained/llc'

test/handler/test_llc_handler.vader

@@ -0,0 +1,56 @@
+Before:
+  runtime! ale_linters/llvm/llc.vim
+
+Execute(llc handler should parse errors output for STDIN):
+  AssertEqual
+  \ [
+  \   {
+  \      'lnum': 10,
+  \      'col': 7,
+  \      'text': "error: value doesn't match function result type 'i32'",
+  \      'type': 'E',
+  \   },
+  \   {
+  \      'lnum': 10,
+  \      'col': 13,
+  \      'text': "error: use of undefined value '@foo'",
+  \      'type': 'E',
+  \   },
+  \ ],
+  \ ale_linters#llvm#llc#HandleErrors(bufnr(''), [
+  \   "llc: <stdin>:10:7: error: value doesn't match function result type 'i32'",
+  \   'ret i64 0',
+  \   '    ^',
+  \   '',
+  \   "llc: <stdin>:10:13: error: use of undefined value '@foo'",
+  \   'call void @foo(i64 %0)',
+  \   '          ^',
+  \ ])
+
+Execute(llc handler should parse errors output for some file):
+  call ale#test#SetFilename('test.ll')
+  AssertEqual
+  \ [
+  \   {
+  \      'lnum': 10,
+  \      'col': 7,
+  \      'text': "error: value doesn't match function result type 'i32'",
+  \      'type': 'E',
+  \   },
+  \   {
+  \      'lnum': 10,
+  \      'col': 13,
+  \      'text': "error: use of undefined value '@foo'",
+  \      'type': 'E',
+  \   },
+  \ ],
+  \ ale_linters#llvm#llc#HandleErrors(bufnr(''), [
+  \   "llc: /path/to/test.ll:10:7: error: value doesn't match function result type 'i32'",
+  \   'ret i64 0',
+  \   '    ^',
+  \   '',
+  \   "llc: /path/to/test.ll:10:13: error: use of undefined value '@foo'",
+  \   'call void @foo(i64 %0)',
+  \   '          ^',
+  \ ])
+