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/configure-gcc.sh

@@ -0,0 +1 @@
+../gcc/configure --target=x86_64-rosetta --prefix=/opt/cross-rosetta --with-sysroot=/Users/wash/projects/rosetta/build/target-root --disable-nls --enable-languages=c,c++ --enable-shared --enable-initfini-array --with-gmp=/opt/homebrew