webos.inc: Fix perf signature changing when perl was or wasn't built
webos.inc: Fix perf signature changing when perl was or wasn't built

:Release Notes:
Fixes error sometimes shown when generating signatures.

:Detailed Notes:
Without this bitbake -S perf shows following error:
ERROR: Bitbake's cached basehash does not match the one we just generated
  (/OE/oe-core/meta/recipes-kernel/perf/perf.bb.do_package)!
if you run it twice, once without perl in sysroot and once with perl
already built

:Testing Performed:
Verified with bitbake -S.

:QA Notes:
No change to image.

:Issues Addressed:
[GF-42606] Ongoing metadata improvement/cleanup work

Open-webOS-DCO-1.0-Signed-off-by: Martin Jansa <martin.jansa@lge.com>
Change-Id: Ie5acbe75c624fa292ead93bb850fd93e529705bb
Reviewed-on: https://g2g.palm.com/4088
Reviewed-by: DCO Verification
Build: Martin Jansa <516df3ff67e1fa5d153800b15fb204c0a1a389dc@lge.com>
Reviewed-by: Martin Jansa <516df3ff67e1fa5d153800b15fb204c0a1a389dc@lge.com>
Tested-by: Martin Jansa <516df3ff67e1fa5d153800b15fb204c0a1a389dc@lge.com>
Reviewed-by: Susan Montooth <be0b8b1fe2cc6a744be9b1ae6516e077aa323e09@lge.com>

openwebos/meta-webos,Garfonso/meta-webos-ports,openwebos/meta-webos,openwebos/meta-webos,Garfonso/meta-webos-ports,nizovn/meta-webos-ports,openwebos/meta-webos,nizovn/meta-webos-ports