gnupg: use native version for signing, rather than one provided by host

Using host gpg has been problematic, and particularly this removes
the need to serialize package creation, as long as --auto-expand-secmem
is passed to gpg-agent, and gnupg >= 2.2.4 is in use
(https://dev.gnupg.org/T3530).

Sadly, gpg-agent itself is single-threaded, so in the longer run
we might want to seek alternatives:
https://lwn.net/Articles/742542/

(a smaller issue is that rpm itself runs the gpg fronted in a serial
fashion, which slows down the build in cases of recipes with very
large amount of packages, e.g. glibc-locale)

Note that sstate signing and verification continues to use host
gpg, as depending on native gpg would create circular dependencies.

[YOCTO #12022]

(From OE-Core rev: 08fef6198122fe79d4c1213f9a64b862162ed6cd)

Signed-off-by: Alexander Kanavin <alexander.kanavin@linux.intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/classes/sign_package_feed.bbclass

@@ -43,4 +43,4 @@ python () {
 }
 
 do_package_index[depends] += "signing-keys:do_deploy"
-do_rootfs[depends] += "signing-keys:do_populate_sysroot"
+do_rootfs[depends] += "signing-keys:do_populate_sysroot gnupg-native:do_populate_sysroot"