godoc/analysis: use build.Default.GOROOT instead of runtime.GOROOT
godoc/analysis: use build.Default.GOROOT instead of runtime.GOROOT

Change-Id: Ic34744557c3fbddd27590303794d384e28ff1ae3
Reviewed-on: https://go-review.googlesource.com/19781
Reviewed-by: Alan Donovan <7069e9552f9d110b0a0f326b96f22f63fb99dfc1@google.com>

golang/tools,syreclabs/go-tools,golang/tools,golang/tools,syreclabs/go-tools,syreclabs/go-tools,golang/tools,syreclabs/go-tools,syreclabs/go-tools,golang/tools,syreclabs/go-tools