Build Swift 4.2-dev on Arch Linux

gistfile1.txt

#!/bin/bash
# Build Swift on Arch Linux
# Original post I followed https://akrabat.com/compiling-swift-on-linux/.

# [1] Checking out repo

mkdir swift-dev
cd swift-dev/
git clone git@github.com:apple/swift.git

cd swift
git checkout -b 4.2-dev origin/swift-4.2-branch
cd ..

# [2] Update the whole source stuff

./swift/utils/update-checkout --clone-with-ssh

# [3] Fix python usage
# Use python2 where appropriate

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"

# [4] Build the whole stuff

./swift/utils/build-script --preset=buildbot_linux,no_test installable_package=~/swift.tar.gz install_destdir=~/.swiftenv/versions/4.2-dev

# [5] Deploy Swift package under Swiftenv

cd ~/.swiftenv/versions
mkdir 4.2-dev
cd 4.2-dev
tar xvzf ~/swift.tar.gz

This script requires python2 !!

For 4.2 release use this command

git fetch --tags
git checkout -b swift-4.2-RELEASE tags/swift-4.2-RELEASE

To avoid python search replaces you can make a python2.7 virtualenv and then reference the correct FindPythonLibs references for the make. To add '--extra-cmake-options=-DPYTHON_EXECUTABLE=/usr/bin/python2.7 -DPYTHON_INCLUDE_DIR=/usr/include/python2.7 -DPYTHON_LIBRARY=/usr/lib/libpython2.7.so -DPYTHON_RELEASE_LIB=/usr/lib/libpython2.7.so' you cannot use a preset but can extract the current preset using the --expand-build-script-invocation toggle and then adding the cmake options ie:

virtualenv -p python2.7 swiftpy
. swiftpy/bin/activate
swift/utils/build-script  --expand-build-script-invocation --preset=buildbot_linux,no_test installable_package=~/swift-4.2.tar.gz install_destdir=~/.swiftenv/versions/4.2
swift/utils/build-script: note: using preset "buildbot_linux,no_test", which expands to 

swift/utils/build-script --assertions --no-swift-stdlib-assertions --swift-enable-ast-verifier=0 --llbuild --swiftpm --xctest --build-ninja --install-swift --install-lldb --install-llbuild --install-swiftpm --install-xctest --install-prefix=/usr '--swift-install-components=autolink-driver;compiler;clang-builtin-headers;stdlib;swift-remote-mirror;sdk-overlay;license;sourcekit-inproc' '--llvm-install-components=llvm-cov;llvm-profdata;IndexStore' --build-swift-static-stdlib --build-swift-static-sdk-overlay --build-swift-stdlib-unittest-extra --test-installable-package --install-destdir=/home/jlawson/.swiftenv/versions/4.2 --installable-package=/home/jlawson/swift-4.2.tar.gz --build-subdir=buildbot_linux --lldb --release --test --validation-test --long-test --stress-test --test-optimized --foundation --libdispatch --lit-args=-v --lldb-test-swift-only --install-foundation --install-libdispatch --reconfigure --skip-test-cmark --skip-test-lldb --skip-test-swift --skip-test-llbuild --skip-test-swiftpm --skip-test-xctest --skip-test-foundation --skip-test-libdispatch --skip-test-playgroundsupport --skip-test-libicu

swift/utils/build-script --assertions --no-swift-stdlib-assertions --swift-enable-ast-verifier=0 --llbuild --swiftpm --xctest --build-ninja --install-swift --install-lldb --install-llbuild --install-swiftpm --install-xctest --install-prefix=/usr '--swift-install-components=autolink-driver;compiler;clang-builtin-headers;stdlib;swift-remote-mirror;sdk-overlay;license;sourcekit-inproc' '--llvm-install-components=llvm-cov;llvm-profdata;IndexStore' --build-swift-static-stdlib --build-swift-static-sdk-overlay --build-swift-stdlib-unittest-extra --test-installable-package --install-destdir=/home/jlawson/.swiftenv/versions/4.2 --installable-package=/home/jlawson/swift-4.2.tar.gz --build-subdir=buildbot_linux --lldb --release --test --validation-test --long-test --stress-test --test-optimized --foundation --libdispatch --lit-args=-v --lldb-test-swift-only --install-foundation --install-libdispatch --reconfigure --skip-test-cmark --skip-test-lldb --skip-test-swift --skip-test-llbuild --skip-test-swiftpm --skip-test-xctest --skip-test-foundation --skip-test-libdispatch --skip-test-playgroundsupport --skip-test-libicu \
 \
'--extra-cmake-options=-DPYTHON_EXECUTABLE=/usr/bin/python2.7 -DPYTHON_INCLUDE_DIR=/usr/include/python2.7 -DPYTHON_LIBRARY=/usr/lib/libpython2.7.so -DPYTHON_RELEASE_LIB=/usr/lib/libpython2.7.so'