Don't brp-strip .ko files

Otherwise SecureBoot signatures may be stripped too.

We used to exclude shared libraries from this strip as they were
supposed to be covered by another brp script (brp-strip-shared), however
it turned out the latter was never really used, so we removed the
exclusion in commit 0ab151a.

As it turns out, that was a little too ambitious, since we may now
inadvertently strip SecureBoot signatures from kernel modules too,
provided that they're made during the build, prior to the invocation of
brp-strip.

Note that this regression currently does *not* affect the following two
cases on Fedora/RHEL systems with redhat-rpm-config installed:

  - in-tree kernel modules; these are built from kernel.spec which
    already contains a hack ensuring that module signing only happens
    *after* any stripping (see %__modsign_install_post in kernel.spec)

  - out-of-tree kernel modules built with debuginfo enabled; this is
    because brp-strip is only called when %debug_package is set to
    %{nil}

Any other combinations may be affected, depending on the macros and
.spec files used, so let's fix this by effectively "reverting" said
commit for .ko files only.

Fixes: rhbz#1967291

scripts/brp-strip

@@ -13,5 +13,5 @@ Darwin*) exit 0 ;;
 esac
 
 # Strip ELF binaries
-find "$RPM_BUILD_ROOT" -type f \! -regex "${RPM_BUILD_ROOT}/*usr/lib/debug.*" -print0 | \
+find "$RPM_BUILD_ROOT" -type f \! -regex "${RPM_BUILD_ROOT}/*usr/lib/debug.*" \! -name "*.ko" -print0 | \
     xargs -0 -r -P$NCPUS -n32 sh -c "file \"\$@\" | sed -n -e 's/^\(.*\):[ 	]*ELF.*, not stripped.*/\1/p' | xargs -I\{\} $STRIP -g \{\}" ARG0