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.

sys/bsp/rosetta.preset/50_bshell

@@ -0,0 +1,8 @@
+[contents]
+"/usr/bin" = [ '/usr/bin/bshell' ]
+"/usr/lib" = [
+	'/usr/lib/libbshell.runtime.so',
+	'/usr/lib/libbshell.core.so',
+]
+
+# vim: ft=toml