This allows the cross compilation of chicken in, at least, the following ways:
```sh
nix-build -A pkgsCross.aarch64-multiplatform.chicken
```
and
```sh
nix-build -A pkgsCross.raspberryPi.chicken
```
Building with clang on x86_64-linux has also been repaired.
Additionally, instead of reimplementing a version tester in the
`installCheckPhase`, this test has been pulled out into its own tester
attribute.
While two broken tests needed to be disabled, the functionality of static
building is not broken. Only the tests themselves seem not to be able to handle
the specification of absolute compiler paths.
6149d31915