Go checker: no longer attempt to redirect output of "go build".

Running "go build -o /dev/null" in a main package that lives in GOPATH
produces an error message:

build output "/dev/null" already exists and is not an object file

This issue won't be addressed on the Go side:

http://code.google.com/p/go/issues/detail?id=4851
https://github.com/golang/go/issues/4851

Consequently, syntastic leaves this to the user to resolve.  Set
g:syntastic_go_go_build_args to something including "-o /some/dir"
to redirect the output of "go build".

plugin/syntastic.vim

@@ -19,7 +19,7 @@ if has('reltime')
     lockvar! g:_SYNTASTIC_START
 endif
 
-let g:_SYNTASTIC_VERSION = '3.6.0-88'
+let g:_SYNTASTIC_VERSION = '3.6.0-89'
 lockvar g:_SYNTASTIC_VERSION
 
 " Sanity checks {{{1

syntax_checkers/go/go.vim

@@ -59,7 +59,7 @@ function! SyntaxCheckers_go_go_GetLocList() dict
         let cleanup = 1
     endif
     let opt_str = (type(opts) != type('') || opts !=# '') ? join(syntastic#util#argsescape(opts)) : opts
-    let makeprg = self.getExec() . ' ' . cmd . ' ' . opt_str . ' ' . syntastic#c#NullOutput()
+    let makeprg = self.getExec() . ' ' . cmd . ' ' . opt_str
 
     " The first pattern is for warnings from C compilers.
     let errorformat =