meta: replace cmake mono-build system with a custom build co-ordinator

every system component now has its own self-contained build system, and a
seed file describing the component and its build system and dependencies.

a new tool, meadow, collects and uses these seed files to build the
components into a full system. meadow also manages the target system root
and a host prefix where toolchain tools are installed to.

the build system has also been updated to use a new $ARCH-rosetta-gcc
compiler, and the patches files necessary to build it have been
added to toolchain/cross-compiler.

meadow

@@ -0,0 +1,18 @@
+#!/bin/bash
+
+SCRIPT_DIR=$( cd -- "$( dirname -- "${BASH_SOURCE[0]}" )" &> /dev/null && pwd )
+
+if [ ! -d "$SCRIPT_DIR/build" ]; then
+	mkdir build
+fi
+
+if [ ! -d "$SCRIPT_DIR/build/meadow_venv" ]; then
+	echo 'Initialising meadow...'
+	python3 -m venv $SCRIPT_DIR/build/meadow_venv
+	source $SCRIPT_DIR/build/meadow_venv/bin/activate
+	pip install -r $SCRIPT_DIR/toolchain/meadow/requirements.txt
+else
+	source $SCRIPT_DIR/build/meadow_venv/bin/activate
+fi
+
+python3 $SCRIPT_DIR/toolchain/meadow/main.py "$@"