gen-lockedsig-cache: Replace glob lookup with hash to filename lookup
Using the glob function to map signatures to sstate files is very slow
when the sstate is large and accessed over nfs. The lookup now only
loads the necessary prefixes and doesn't use glob as all.
Unfortunately I don't have access to the systems where the performance
isse was noticed and on my test system the glob is fast enough that
the performance numbers aren't useful. I could verify that file list
returned by the new code is the same.
[YOCTO #13539]
Signed-off-by: Konrad Scherer <Konrad.Scherer@windriver.com> Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
