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.

toolchain/cross-compiler/build.py

@@ -0,0 +1,31 @@
+import os
+
+class Builder:
+    def get_prefix(self):
+        return os.environ.get('MEADOW_NATIVE_ROOT', None)
+
+
+    def get_target(self):
+        env = os.environ
+        target = os.environ.get('MEADOW_TARGET_PLATFORM', None)
+        parts = target.split('-')
+        return f'{parts[0]}-rosetta'
+
+
+    def download(self):
+        pass
+
+
+    def configure(self):
+        pass
+
+
+    def build(self):
+        pass
+
+
+    def install(self):
+        pass
+
+
+print(f'building cross compiler for {get_gcc_target()}, installed to {get_prefix()}')