compiler: don't export bodies for functions marked "go:noinline"

compiler: don't export bodies for functions marked "go:noinline"

    The current Mark_inline_candidates helper looks only at budget when
    deciding to mark a function or method as inline (with the proviso that
    IR constructs not yet supported by the inliner are given artificially
    high cost). This patch changes the helper to also look at whether a
    function has the "go:noinline" pragma; if it does have the pragma
    there is no point putting it into the export data (it will just make
    the export data bigger).

    Reviewed-on: https://go-review.googlesource.com/c/gofrontend/+/186923

From-SVN: r273611