classes/cpan-base: fix signatures changing when perl is in sysroot
The previous fix for this same issue (OE-Core rev
f31f6a70ec24e8c9515d69c5092e15effc5e7d4d) was not sufficient - we are
setting the PERLVERSION variable from the get_perl_version function, but
we're setting it using immediate expansion; thus the value is going into
the signature and is still different between the time the recipe is
cached on an empty TMPDIR and after perl is in the sysroot and we run
bitbake -S perf. We could remove the immediate expansion, but that would
mean the get_perl_version function would be called more often, so just set
vardepvalue on the PERLVERSION variable to fix the problem instead.
Signed-off-by: Paul Eggleton <paul.eggleton@linux.intel.com>
Signed-off-by: Saul Wold <sgw@linux.intel.com>
