testsuite: export environment with flags and LD_PRELOAD
testsuite: export environment with flags and LD_PRELOAD

A certain config can add flags and each flag may be associated with a
lib to LD_PRELOAD. It's now done for uname(2), which requires uname.so
in order to trap the calls.

Other trap will be added in later commits.

lpereira/kmod,Distrotech/kmod,lucasdemarchi/kmod,Distrotech/kmod,lucasdemarchi/kmod,lpereira/kmod,pmmccorm/kmod,lucasdemarchi/kmod,pmmccorm/kmod,lpereira/kmod,pmmccorm/kmod,Distrotech/kmod