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.

arch/x86_64/command/run-kernel.command

@@ -0,0 +1,12 @@
+[command]
+name = 'run-kernel'
+description = 'Run the kernel image directly under QEMU'
+
+[dependency]
+commands = [ 'qemu-system-x86_64' ]
+seeds = [ 'magenta', 'bsp' ]
+
+[exec]
+args = [ 'src:run-kernel.py']
+
+# vim: ft=toml