add a few libs as BuildRequire that are required or optional for selftests

While skimming the build logs for an unrelated problem I noticed a few errors and warnings in the selftest sections due to required or optional dependencies missing. These fix them.

FWIW, in case anyone cares: There were a few compiler errors in the selftest section of kernel.spec before these changes that still occur after applying them (at least when building on Fedora; just search for '] Errror' in the build logs). There for example are still several of these on x86_64 (and similar ones on aarch64):

relocation R_X86_64_32 against `.rodata' can not be used when making a PIE object; recompile with -fPIE

Signed-off-by: Thorsten Leemhuis fedora@leemhuis.info