scripts/bootstrap.sh: tool for bootstrapping alpine

utility to do initial cross-compiler, and cross build of base
packages for new architectures.

scripts/bootstrap.sh

+#!/bin/sh
+
+TARGET_ARCH="$1"
+SUDO_APK=abuild-apk
+
+# optional cross build packages
+KERNEL_PKG="linux-firmware linux-vanilla"
+
+# get abuild configurables
+[ -e /usr/share/abuild/functions.sh ] || (echo "abuild not found" ; exit 1)
+CBUILDROOT="$(CTARGET=$TARGET_ARCH . /usr/share/abuild/functions.sh ; echo $CBUILDROOT)"
+. /usr/share/abuild/functions.sh
+[ -z "$CBUILD_ARCH" ] && die "abuild is too old (use git snapshot from cross-build branch)"
+
+# deduce aports directory
+[ -z "$APORTS" ] && APORTS=$(realpath $(dirname $0)/../)
+[ -e "$APORTS/main/build-base" ] || die "Unable to deduce aports base checkout"
+
+apkbuildname() {
+	echo $APORTS/main/$1/APKBUILD
+}
+
+msg() {
+	[ -n "$quiet" ] && return 0
+	local prompt="$GREEN>>>${NORMAL}"
+	local name="${BLUE}bootstrap-${TARGET_ARCH}${NORMAL}"
+        printf "${prompt} ${name}: %s\n" "$1" >&2
+}
+
+setup_sysroot() {
+	[ -e "$CBUILDROOT" ] && return 0
+	msg "Creating sysroot in $CBUILDROOT"
+	mkdir -p "$CBUILDROOT/etc/apk/keys"
+	cp -a /etc/apk/keys/* "$CBUILDROOT/etc/apk/keys"
+	${SUDO_APK} add --quiet --initdb --arch $TARGET_ARCH --root $CBUILDROOT
+}
+
+create_cross_compiler() {
+	msg "Building cross-compiler"
+
+	# Prepare local build environment
+	apk info --quiet --installed build-base gcc-gnat || ${SUDO_APK} add build-base gcc-gnat
+
+	# Build and install cross binutils (--with-sysroot)
+	CTARGET=$TARGET_ARCH APKBUILD=$(apkbuildname binutils) abuild up2date >& /dev/null
+	if [ $? -ne 0 ]; then
+		CTARGET=$TARGET_ARCH APKBUILD=$(apkbuildname binutils) abuild -r || return 1
+		${SUDO_APK} add --repository "$REPODEST/main" binutils-$TARGET_ARCH || return 1
+	fi
+
+	# Build and install cross GCC
+	CTARGET=$TARGET_ARCH APKBUILD=$(apkbuildname gcc) abuild up2date >& /dev/null
+	if [ $? -ne 0 ]; then
+		# Build bootstrap C-library for target if needed
+		CHOST=$TARGET_ARCH BOOTSTRAP=nolibc APKBUILD=$(apkbuildname musl) abuild up2date >& /dev/null
+		if [ $? -ne 0 ]; then
+			# musl does not need GCC for headers installation, skipped step.
+			# CTARGET=$TARGET_ARCH BOOTSTRAP=noheaders abuild
+
+			# Hack: Install C-library headers for target sysroot
+			CHOST=$TARGET_ARCH BOOTSTRAP=nolibc APKBUILD=$(apkbuildname musl) abuild clean unpack prepare install_sysroot_headers || return 1
+
+			# Build minimal cross GCC (--with-newlib --enable-threads=no --disable-bootstrap)
+			CTARGET=$TARGET_ARCH BOOTSTRAP=nolibc APKBUILD=$(apkbuildname gcc) abuild -r || return 1
+
+			# Cross build bootstrap C-library for the target
+			${SUDO_APK} --quiet del gcc-$TARGET_ARCH g++-$TARGET_ARCH gcc-gnat-$TARGET_ARCH
+			${SUDO_APK} add --repository "$REPODEST/main" gcc-pass2-$TARGET_ARCH || return 1
+			CHOST=$TARGET_ARCH BOOTSTRAP=nolibc APKBUILD=$(apkbuildname musl) abuild -r || return 1
+			${SUDO_APK} --quiet del gcc-pass2-$TARGET_ARCH
+		fi
+
+		# Build cross GCC
+		apk info --quiet --installed --root "$CBUILDROOT" musl-dev || \
+			${SUDO_APK} --root "$CBUILDROOT" add --repository "$REPODEST/main" musl-dev \
+			|| return 1
+		CTARGET=$TARGET_ARCH APKBUILD=$(apkbuildname gcc) abuild -r || return 1
+		${SUDO_APK} add --repository "$REPODEST/main" gcc-gnat gcc-$TARGET_ARCH g++-$TARGET_ARCH gcc-gnat-$TARGET_ARCH \
+			|| return 1
+	fi
+}
+
+cross_compile_base() {
+	msg "Cross building base system"
+
+	# remove possible old pass2 gcc, and add implicit host prerequisite packages
+	apk info --quiet --installed gcc-pass2-$TARGET_ARCH && ${SUDO_APK} del gcc-pass2-$TARGET_ARCH
+	apk info --quiet --installed gcc-gnat gcc-$TARGET_ARCH g++-$TARGET_ARCH gcc-gnat-$TARGET_ARCH || \
+		${SUDO_APK} add --repository "$REPODEST/main" gcc-gnat gcc-$TARGET_ARCH g++-$TARGET_ARCH gcc-gnat-$TARGET_ARCH \
+		|| return 1
+	apk info --quiet --installed --root "$CBUILDROOT" libgcc musl-dev || \
+		${SUDO_APK} --root "$CBUILDROOT" add --repository "$REPODEST/main" libgcc musl-dev \
+		|| return 1
+
+	# ordered cross-build
+	for PKG in fortify-headers linux-headers musl libc-dev \
+		   busybox busybox-initscripts binutils make pkgconf \
+		   zlib openssl libfetch apk-tools \
+		   gmp mpfr3 mpc1 isl cloog gcc \
+		   openrc alpine-conf alpine-baselayout alpine-keys alpine-base build-base \
+		   attr libcap patch sudo acl fakeroot tar \
+		   pax-utils abuild openssh \
+		   ncurses util-linux lvm2 popt xz cryptsetup kmod lddtree mkinitfs \
+		   $KERNEL_PKG ; do
+
+		CHOST=$TARGET_ARCH BOOTSTRAP=bootimage APKBUILD=$(apkbuildname $PKG) abuild -r || exit 1
+
+		case "$PKG" in
+		fortify-headers | libc-dev | build-base)
+			# headers packages which are implicit but mandatory dependency
+			apk info --quiet --installed --root "$CBUILDROOT" $PKG || \
+				${SUDO_APK} --update --root "$CBUILDROOT" --repository "$REPODEST/main" add $PKG \
+				|| return 1
+			;;
+		musl | gcc)
+			# target libraries rebuilt, force upgrade
+			[ "$(apk upgrade --root "$CBUILDROOT" --repository "$REPODEST/main" --available --simulate | wc -l)" -gt 1 ] &&
+				${SUDO_APK} upgrade --root "$CBUILDROOT" --repository "$REPODEST/main" --available
+			;;
+		esac
+	done
+}
+
+if [ -z "$TARGET_ARCH" ]; then
+	local program=$(basename $0)
+	cat <<EOF
+usage: $program TARGET_ARCH
+
+This script creates a local cross-compiler, and uses it to
+cross-compile an Alpine Linux base system for new architecture.
+
+Steps for introducing new architecture include:
+- adding the compiler tripler and arch type to abuild
+- adding the arch type detection to apk-tools
+- adjusting build rules for packages that are arch aware:
+  gcc, openssl, linux-headers
+- create new kernel config for linux-vanilla
+
+After these steps the initial cross-build can be completed
+by running this with the target arch as parameter, e.g.:
+	./$program aarch64
+
+EOF
+	return 1
+fi
+
+setup_sysroot && create_cross_compiler && cross_compile_base