compiler: don't report runtime escapes if we've seen errors

compiler: don't report runtime escapes if we've seen errors

    If we get errors during compilation, we skip the escape analysis pass.
    If we are compiling the runtime package, we report an error if a bound
    method expression escapes.  The effect is that if we get an error
    while compiling the runtime package, we would report confusing and
    meaningless errors about bound method expressions escaping.

    This CL stops doing that.

    Reviewed-on: https://go-review.googlesource.com/c/gofrontend/+/192720

From-SVN: r275238