Revert "Enable strip again"

This reverts commit 52acad4b66ff6fb11f09957b73f437038bd081be.

This solves two issues:

1) Build breaks when compiling with multiple jobs (`make -j2` or higher)

2) Building non-stripped binaries is not possible without changing the Makefile, which most people are not comfortable with.

More detail on the last issue: On f.i. Gentoo Linux, you can simple install something by typing `emerge foo`; this creates stripped binaries because the package manger handles that. If you want to debug something, you can type `FEATURES="nostrip" emerge foo`, and you'll have non-stripped binaries. Not with rdup though, because it insists on stripping, not leaving a choice for the end user.