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.
This will ensure that Hydra attempts to build the eggs on all supported
platforms instead of just the platform the evaluator is running
on (currently x86_64-linux).
Also updates the matchable egg (used by egg2nix) from 1.0 -> 1.1 and
removes trailing slashes from the path prefix variables passed to
wrapProgram (they're unnecessary and only result in doubled-up slashes
in the values).
