When installing profiling tools on Mac OS X print
message if there is a problem with /usr/local/bin
Fixes#2209.
R=golang-dev, r, adg
CC=golang-dev, mike.rosset
https://golang.org/cl/4950057
the bash scripts and makefiles for building go didn't take into account
the fact $GOROOT / $GOBIN could both be directories containing whitespaces,
and was not possible to build it in such a situation.
this commit adjusts the various makefiles/scripts to make it aware of that
possibility, and now it builds successfully when using a path with whitespaces
as well.
Fixes#115.
R=rsc, dsymonds1
https://golang.org/cl/157067
