Provide at least some support for build from Arch.

README.md

@@ -10,7 +10,7 @@ Of course, you do need to have the requisite build tooling installed... in addit
 
 (At this point I will note, as this has come up multiple times: it is neither practical nor appropriate for Orchid's documentation to detail how to install any of these toolchains. The instructions are different for every operating system, are different for every single distribution of Linux, and are often even different for specific versions of a distribution. FWIW, developers already have most of this software installed; and, if you don't, these projects have their own documentation.)
 
-That said, the "usual algorithm" of "try to build it, and if you get an error saying you are missing X, just install X" should work, so I'd just dive in (like, honestly, I'm shocked you are reading this); that said, if you are "feeling lucky", you can run env/setup-mac.sh (if using macOS) or env/setup-lnx.sh (if using Ubuntu), which are scripts that install everything on either macOS or (specifically and only) Ubuntu (and thereby can serve as "documentation" if you refuse to just dive in).
+That said, the "usual algorithm" of "try to build it, and if you get an error saying you are missing X, just install X" should work, so I'd just dive in (like, honestly, I'm shocked you are reading this); that said, if you are "feeling lucky", you can run env/setup-mac.sh (if using macOS) or env/setup-lnx.sh (if using Ubuntu/Arch), which are scripts that install everything on either macOS or (specifically and only) Ubuntu (and thereby can serve as "documentation" if you refuse to just dive in).
 
 Given that you have a box capable of compiling other projects (as we aren't using anything "weird", really... meson is probably the rarest dependency we have, and it will be extremely obvious) you can then just go into any subfolder you want (such as app-{android,ios}, or cli-shared/srv-daemon and run "make". Seriously: it's that easy... if it breaks for some reason other than "you ran out of memory / disk space" or "command X not found" (which you can trivially solve), please file an issue.
 

env/lnx-arch.sh

@@ -0,0 +1,19 @@
+#!/bin/bash
+set -e
+
+pacman -Sy \
+    ubuntu-keyring \
+    bc tcl vim \
+    curl git rsync wget \
+    fakeroot talloc \
+    cpio rpm-tools unzip zstd \
+    clang lld llvm \
+    binutils aarch64-linux-gnu-binutils \
+    libc++ libc++abi \
+    python-pip python-setuptools \
+    jdk17-openjdk \
+    bison flex gperf \
+    gettext groff texinfo \
+    autoconf autoconf-archive automake \
+    libtool meson ninja pkgconf \
+    qemu-system-{x86,aarch64} \

env/setup-apt.sh → env/lnx-ubuntu.sh

@@ -5,20 +5,21 @@ export DEBIAN_FRONTEND=noninteractive
 apt-get update
 
 apt-get -y install \
+    ubuntu-keyring \
     bc tcl xxd \
     curl git-core rsync wget \
     fakeroot libtalloc-dev \
     cpio rpm unzip zstd \
     clang clang-tidy lld llvm \
-    binutils-{aarch64,x86-64}-linux-gnu \
+    binutils-{x86-64,aarch64}-linux-gnu \
     libc++-dev libc++abi-dev \
-    g++-multilib gcc-multilib \
     python3-pip python3-setuptools \
     openjdk-11-jre-headless \
     bison flex gperf \
     gettext groff texinfo \
     autoconf autoconf-archive automake \
     libtool ninja-build pkg-config \
+    qemu-system-{x86,arm} \
 
 function usable() {
     # Ubuntu bionic ships meson 0.45, which is too old to build glib

env/setup-lnx.sh

@@ -7,6 +7,7 @@ else
     sudo=(sudo -EH)
 fi
 
-"${sudo[@]}" env/setup-apt.sh
+. /etc/os-release
+"${sudo[@]}" "env/lnx-${ID}.sh"
 
 env/setup-all.sh

env/uname.mk

@@ -13,6 +13,6 @@ uname-m := $(shell uname -m)
 uname-s := $(shell uname -s)
 uname-o := $(shell uname -o 2>/dev/null)
 
-objcopy = $(host/$*)-objcopy
+objcopy = $(shell which $(host/$*)-objcopy objcopy 2>&1 | head -n1)
 
 -include $(pwd)/uname-$(uname-s).mk