This reverts commit 41af38f3728bd64b80721c44ed1fb019978cbc1b, reversing
changes made to f0fec244ca380b9d3e617ee7b419c59758c8b0f1.
Let's delay this. We have some serious regressions.
Whenever we create scripts that are installed to $out, we must use runtimeShell
in order to get the shell that can be executed on the machine we create the
package for. This is relevant for cross-compiling. The only use case for
stdenv.shell are scripts that are executed as part of the build system.
Usages in checkPhase are borderline however to decrease the likelyhood
of people copying the wrong examples, I decided to use runtimeShell as well.
