Merge pull request #27215 from obsidiansystems/stdenv-harden

--- swift/utils/build-script-impl	2017-01-23 12:47:20.401326309 -0600

+++ swift-pax/utils/build-script-impl	2017-01-23 13:24:10.339366996 -0600

@@ -1823,6 +1823,16 @@ function set_lldb_xcodebuild_options() {

@@ -1823,6 +1823,17 @@ function set_lldb_xcodebuild_options() {

     fi

 }

+## XXX: Taken from nixpkgs /pkgs/stdenv/generic/setup.sh

+isELF() {

+    local fn="$1"

+    local fd

+    local magic

+    exec {fd}< "$fn"

+    read -n 4 -u $fd magic

    shift

    local var="$hookName"

    if [[ "$hookName" =~ Hook$ ]]; then var+=s; else var+=Hooks; fi

    eval "local -a dummy=(\"\${$var[@]}\")"

    for hook in "_callImplicitHook 0 $hookName" "${dummy[@]}"; do

    local -n var

    local hook

    for hook in "_callImplicitHook 0 $hookName" "${var[@]}"; do

        _eval "$hook" "$@"

    done

    return 0

    shift

    local var="$hookName"

    if [[ "$hookName" =~ Hook$ ]]; then var+=s; else var+=Hooks; fi

    eval "local -a dummy=(\"\${$var[@]}\")"

    for hook in "_callImplicitHook 1 $hookName" "${dummy[@]}"; do

    local -n var

    local hook

    for hook in "_callImplicitHook 1 $hookName" "${var[@]}"; do

        if _eval "$hook" "$@"; then

            return 0

        fi

# Return success if the specified file is an ELF object.

isELF() {

    local fn="$1"

    local fd

    local magic

    exec {fd}< "$fn"

    read -n 4 -u $fd magic

# "#!").

isScript() {

    local fn="$1"

    local fd

    local magic

    if ! [ -x /bin/sh ]; then return 0; fi

    exec {fd}< "$fn"