This substitution produces a nix-build warning, because the target
string was removed in commit 7b225df9a492977b8fff0948ce93c5ab31766f64
in 2016.
Remove the substition from the `postPatch` phase in `sbcl/common.nix`.
- Remove some debugging output at the start of the `patchPhase` section,
which appears to have outlived its value.
- Rename `patchPhase` to `postPatch`, to avoid preventing people adding
patches via the `patches` variable.
- Add `preBuild` and `postBuild` run-hooks to the `buildPhase` section.
- Add `preInstall` and `postInstall` run-hooks to the `installPhase`
section.
The sbcl version specific nix expressions were an exact copy of each
other with the version and hash swapped out, leading to unnecessary code
duplication. This has been resolved by moving the common expression to
common.nix and only tracking version and hash in the version specific
expressions.
Since the expression is unchanged, this should cause 0 rebuilds.
