main/cyrus-sasl: (db_gdbm) fix gdbm_errno overlay from gdbm_close

gdbm_close also sets gdbm_errno since version 1.17.
This leads to a problem in libsasl as the gdbm_close incovation overlays
the gdbm_errno value which is then later used for the error handling.

Upstream: https://github.com/cyrusimap/cyrus-sasl/pull/554
7 jobs for !18576 with cyrus-sasl-dbm-errno in 2 minutes and 35 seconds
detached
Status Job ID Name Coverage
  Lint
passed #330881
docker-alpine x86_64
lint

00:00:18

 
  Build
passed #330886
docker-alpine ci-build aarch64
build-aarch64

00:01:27

passed #330887
docker-alpine ci-build armv7
build-armv7

00:01:35

passed #330885
docker-alpine ci-build ppc64le
build-ppc64le

00:01:41

passed #330884
docker-alpine ci-build s390x
build-s390x

00:01:29

passed #330883
docker-alpine ci-build x86
build-x86

00:00:56

passed #330882
docker-alpine ci-build x86_64
build-x86_64

00:00:46