misc/pprof: fix address lookup regression on Linux
misc/pprof: fix address lookup regression on Linux

Just use "go tool addr2line" no matter what, since we know
it works for all OSs.

Fixes issue 4818.

R=rsc, r
CC=golang-dev
https://codereview.appspot.com/7526047

Committer: Rob Pike <4dc7c9ec434ed06502767136789763ec11d2c4b7@golang.org>

apparentlymart/golang,tv42/old-go,tv42/old-go,gnanderson/go,gnanderson/go,tv42/old-go,apparentlymart/golang,dsriram/golang,pombredanne/go-deleteme,gnanderson/go,gnanderson/go,apparentlymart/golang,tv42/old-go,dsriram/golang,dsriram/golang,gnanderson/go,gnanderson/go,apparentlymart/golang,dsriram/golang,pombredanne/go-deleteme,apparentlymart/golang,pombredanne/go-deleteme,tv42/old-go,gnanderson/go,apparentlymart/golang,pombredanne/go-deleteme,pombredanne/go-deleteme,tv42/old-go,pombredanne/go-deleteme,dsriram/golang,apparentlymart/golang,pombredanne/go-deleteme,dsriram/golang,dsriram/golang,tv42/old-go