[OE-core] oprofile rebuilds for different MACHINES (sstate)

[Denys Dmytriyenko]

So, I've been debugging the issue of oprofile rebuilding from one MACHINE to 
another (causing PR issues, etc). I was able to trace it down to this line:

EXTRA_OECONF = "--with-kernel=${STAGING_KERNEL_DIR}  --without-x ac_cv_prog_XSLTPROC="

And STAGING_KERNEL_DIR resolves to this:

STAGING_KERNEL_DIR = "${TMPDIR}/work-shared/${MACHINE}/kernel-source"

Now, obviously, when MACHINE changes, sstate invalidates do_configure and 
rebuilds oprofile.

The question is, what is the proper fix in this case - mark oprofile as 
machine-specific with PACKAGE_ARCH = "${MACHINE_ARCH}", since it will be 
configuring and building against (potentially) completely different kernel 
tree. So, just mark it explicitly and be safe...

Or another option is to tell sstate to ignore changes to the above variables 
with this simple line:

EXTRA_OECONF[vardepsexclude] = "STAGING_KERNEL_DIR"

This also does the trick, but I'm a bit worried there could be side-effects of 
using oprofile against the wrong kernel... Any recommendations?

-- 
Denys