Build Swift 5.x snapshot on Arch Linux

buid_swift_snapshot.sh

#!/bin/bash
# SNAPSHOT=5.1-DEVELOPMENT-SNAPSHOT-2019-09-16-a
SNAPSHOT=5.1-RELEASE

if [ ! -d swift ]
then
    echo Please clone Swift language source
    echo run
    echo   git clone https://github.com/apple/swift.git
    echo or
    echo   git clone git@github.com:apple/swift.git
    echo if you already have a github account

    exit 1
fi

# Fall-back to default path set
# to avoid interferences
unset PATH
. /etc/profile

# Fetch dependencies
python2 ./swift/utils/update-checkout --tag=swift-${SNAPSHOT} --clone-with-ssh

# Fix python2 usage
# TODO Check if python --version >= 3.x.y first
#./fix_python_usage.sh
# Use python2 where appropriate - on Arch Linux Python 3.x is the default breaking the build process
srcdir="."
find "$srcdir" -type f -print0 | \
    xargs -0 sed -i 's|/usr/bin/env python$|&2|;s|/usr/bin/python$|&2|'
find "$srcdir/lldb" -name Makefile -print0 | \
    xargs -0 sed -i 's|python-config|python2-config|g'
sed -i '/^cmake_minimum_required/a set(Python_ADDITIONAL_VERSIONS 2.7)' \
    "$srcdir/swift/CMakeLists.txt"
sed -i '/^cmake_minimum_required/a set(Python_ADDITIONAL_VERSIONS 2.7)' \
    "$srcdir/lldb/CMakeLists.txt"
sed -i 's/\<python\>/&2/' \
    "$srcdir/swift/utils/build-script-impl" \
    "$srcdir/swift/test/sil-passpipeline-dump/basic.test-sh"

# Fix wrong glibc include paths in glibc module map
# ( cd swift && patch -p1 -i "../glibc-includes.patch" )

# Build the whole stuff
./swift/utils/build-script \
    --preset=buildbot_linux,no_test \
    installable_package=~/swift-${SNAPSHOT}.tar.gz \
    install_destdir=~/.swiftenv/versions/${SNAPSHOT}