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/debug.command

@@ -0,0 +1,5 @@
+[command]
+name = 'debug'
+description = 'Run the system under a debugger'
+
+# vim: ft=toml

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

arch/x86_64/command/run-kernel.py

@@ -0,0 +1,30 @@
+import os
+import shutil
+import subprocess
+
+sysroot = os.environ['MEADOW_SYSROOT']
+native_root = os.environ['MEADOW_NATIVE_ROOT']
+tmp = os.environ['MEADOW_TEMP']
+
+bsp = os.path.join(sysroot, 'boot', 'rosetta-system.bsp')
+kernel_exe = os.path.join(sysroot, 'boot', 'magenta_kernel')
+kernel_exe_elf32 = os.path.join(tmp, 'magenta_kernel.elf32')
+e64patch = os.path.join(native_root, 'bin', 'e64patch')
+
+shutil.copyfile(kernel_exe, kernel_exe_elf32)
+subprocess.run([ e64patch, kernel_exe_elf32 ])
+
+qemu_args = [
+        'qemu-system-x86_64',
+        '-m', '128M',
+        '-cpu', 'qemu64,+rdrand',
+        '-kernel', kernel_exe_elf32,
+        '-initrd', bsp,
+        '-serial', 'stdio',
+        '--append', 'kernel.early-console=ttyS0'
+]
+
+try:
+    subprocess.run(qemu_args)
+except KeyboardInterrupt:
+    pass