CMake usually requires all libraries required for linking to be
specified at CMake configure time. However, in Rust native dependencies
may be specified inside the source code via the [`link`] attribute.
`rustc` can be instructed to print all required native libraries at
build time, however this is already after the CMake configure stage
has finished. To work around this we wrap the build command for Rust
static libraries in a wrapper script, that parses the required libraries
from the `rustc` output and writes them into an `rsp` file.
At configure time we can then instruct CMake to read the linker
arguments from the file that our wrapper will generate later at build
time.

[`link`]: https://doc.rust-lang.org/reference/items/external-blocks.html#the-link-attribute