missing dependency lib.pm for scan-build's c++-analyzer

[dkl]

Hi,

The internal c++-analyzer script from scan-build uses lib.pm, so perl-module-lib should probably be added as RDEPENDS of clang-tools. Because it was missing, there were Can't locate lib.pm in @INC errors when running scan-build on C++ sources. This showed up here with kirkstone with scan-build from nativesdk-clang in a Yocto SDK, but I've checked and it still happens with nativesdk-clang-tools in a Yocto SDK built from current poky + meta-clang master.

If you want I can send a patch for this (and also for kirkstone), although I'm surprised it did not show up earlier in #777. Perhaps because it appears to be C++-specific.