code review 4249045: build: move $GOBIN ahead of /bin, /usr/bin in build $PATH

src/env.bash

 #!/usr/bin/env bash
 # Copyright 2009 The Go Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style
 # license that can be found in the LICENSE file.
 
 export GOROOT=${GOROOT:-$(cd ..; pwd)}
 
 if ! test -f "$GOROOT"/include/u.h
 then
         echo '$GOROOT is not set correctly or not exported: '$GOROOT 1>&2
@@ skipping 11 matching lines @@
 fi
 
 export GOBIN=${GOBIN:-"$GOROOT/bin"}
 if [ ! -d "$GOBIN" -a "$GOBIN" != "$GOROOT/bin" ]; then
         echo '$GOBIN is not a directory or does not exist' 1>&2
         echo 'create it or set $GOBIN differently' 1>&2
         exit 1
 fi
 
 export OLDPATH=$PATH
-export PATH=/bin:/usr/bin:"$GOBIN":$PATH
+export PATH="$GOBIN":/bin:/usr/bin:$PATH
 
 MAKE=make
 if ! make --version 2>/dev/null | grep 'GNU Make' >/dev/null; then
         MAKE=gmake
 fi
 
 # Tried to use . <($MAKE ...) here, but it cannot set environment
 # variables in the version of bash that ships with OS X.  Amazing.
 eval $($MAKE --no-print-directory -f Make.inc go-env | egrep 'GOARCH|GOOS|GOHOSTARCH|GOHOSTOS|GO_ENV')
 
 # Shell doesn't tell us whether make succeeded,
 # so Make.inc generates a fake variable name.
 if [ "$MAKE_GO_ENV_WORKED" != 1 ]; then
         echo 'Did not find Go environment variables.' 1>&2
         exit 1
 fi
 unset MAKE_GO_ENV_WORKED