Add simple script for detecting the bashbrew architecture of a system

Author: tianon

scripts/bashbrew-host-arch.sh

@@ -0,0 +1,55 @@
+#!/usr/bin/env bash
+set -Eeuo pipefail
+
+found() {
+	echo "$@"
+	exit
+}
+
+arch=
+if command -v apk > /dev/null && tryArch="$(apk --print-arch)"; then
+	arch="$tryArch"
+elif command -v dpkg > /dev/null && tryArch="$(dpkg --print-architecture)"; then
+	arch="${tryArch##*-}"
+elif command -v uname > /dev/null && tryArch="$(uname -m)"; then
+	echo >&2 "warning: neither of 'dpkg' or 'apk' found, falling back to 'uname'"
+	arch="$tryArch"
+
+	os="$(uname -o 2>/dev/null || :)"
+	case "$os" in
+		Cygwin | Msys)
+			# TODO support non-amd64 Windows
+			found 'windows-amd64'
+			;;
+	esac
+fi
+
+case "$arch" in
+	amd64 | x86_64)    found 'amd64'    ;;
+	arm64 | aarch64)   found 'arm64v8'  ;;
+	armel)             found 'arm32v5'  ;;
+	armv7)             found 'arm32v7'  ;;
+	i[3456]86 | x86)   found 'i386'     ;;
+	mips64el)          found 'mips64le' ;; # TODO "uname -m" is just "mips64" (which is also "apk --print-arch" on big-endian MIPS) so we ought to disambiguate that somehow
+	ppc64el | ppc64le) found 'ppc64le'  ;;
+	riscv64)           found 'riscv64'  ;;
+	s390x)             found 's390x'    ;;
+
+	armhf)
+		if [ -s /etc/os-release ] && id="$(grep -Em1 '^ID=[^[:space:]]+$' /etc/os-release)"; then
+			eval "$id"
+			case "${ID:-}" in
+				alpine | raspbian) found 'arm32v6' ;;
+				*)                 found 'arm32v7' ;;
+			esac
+		else
+			echo >&2 "warning: '$arch' is ambiguous (and '/etc/os-release' is missing 'ID=xxx'), assuming 'arm32v6' for safety"
+			found 'arm32v6'
+		fi
+		;;
+
+	*)
+		echo >&2 "error: unknown architecture: '$arch'"
+		exit 1
+		;;
+esac