Fix cross compilation and build for sandboxes enviroments.

[levydsa]

Build scripts shouldn't write to anything but OUT_DIR. So, instead of copying sqlite3.c to sqlite3mc in source, copy it to OUT_DIR and build from there.

https://doc.rust-lang.org/cargo/reference/build-scripts.html#outputs-of-the-build-script

Build scripts may save any output files or intermediate artifacts in the directory specified in the OUT_DIR environment variable. Scripts should not modify any files outside of that directory.

On some environments, Nix derivations, the permissions of source files are limited, and get copied over using the standard fs::copy. To prevent this, cp --no-preserve=mode,ownership is needed. Inside a Nix derivation, some coreutils are overridden and this is fine to use even on a MacOS device. To make this more reliable, if the cp command fails, do a normal copy with fs functions.

Some CMake configuration was added to allow cross-compilation of sqlite3mc for more targets.

[levydsa]

The copy_with_cp name is a bit misleading, but should be fine. Maybe changing it to just copy is better?