RFR: JDK-8217723 Switch ld from bfd to gold on gcc toolchain

[Martin Buchholz]

Another, more productionized, version of my benchmark:

processors=12
g++ (Debian 7.3.0-5) 7.3.0
--- -fuse-ld=bfd ---
6.559 user 1.180 system 7.740 total
--- -fuse-ld=gold ---
4.575 user 0.600 system 5.176 total
--- -fuse-ld=gold -Wl,-threads ---
9.355 user 5.062 system 4.289 total
--- -fuse-ld=lld ---
2.700 user 1.058 system 1.157 total
--- -fuse-ld=lld -Wl,-threads ---
2.572 user 1.128 system 1.107 total


#!/bin/bash
set -eu
echo processors=$(nproc)
read -a CMDLINE < $(find . -name BUILD_LIBJVM_link.cmdline -print)

readonly DRIVER="${CMDLINE[0]}"
"$DRIVER" --version | head -1

benchmark() {
  echo --- "$@" ---
  local -r TIMEFORMAT="%U user %S system %R total"
  time "$DRIVER" "$@" "${CMDLINE[@]:1}"
}

benchmark -fuse-ld=bfd
benchmark -fuse-ld=gold
benchmark -fuse-ld=gold -Wl,-threads
benchmark -fuse-ld=lld
benchmark -fuse-ld=lld -Wl,-threads