spec: use pkgconf to find out krb5 version

In Fedora 33 RPM migrated to use SQLITE as its database format. When
COPR builders run on Fedora 33 and build a package for older Fedora
version that uses RPM with BDB backend, RPM inside the build environment
will not be able to open its own database (SQLITE).

Replace use of RPM to discover krb5 version by use of pkgconf which
provides the same output but doesn't need to look into RPM database.

Signed-off-by: Alexander Bokovoy <abokovoy@redhat.com>
Reviewed-By: Rob Crittenden <rcritten@redhat.com>

freeipa.spec.in

@@ -143,7 +143,7 @@
 # https://bugzilla.redhat.com/show_bug.cgi?id=1345975#c20
 %global sssd_version 1.16.3-2
 
-%define krb5_base_version %(LC_ALL=C rpm -q --qf '%%{VERSION}' krb5-devel | grep -Eo '^[^.]+\.[^.]+')
+%define krb5_base_version %(LC_ALL=C pkgconf --modversion krb5 | grep -Eo '^[^.]+\.[^.]+' || echo %krb5_version)
 
 %if 0%{?fedora} >= 33
 # systemd with resolved enabled
@@ -185,6 +185,7 @@ BuildRequires:  openldap-devel
 # DAL version change may cause code crash or memory leaks, it is better to fail early.
 BuildRequires:  krb5-kdb-version = %{krb5_kdb_version}
 BuildRequires:  krb5-devel >= %{krb5_version}
+BuildRequires:  pkgconfig(krb5)
 %if 0%{?with_ipa_join_xml}
 # 1.27.4: xmlrpc_curl_xportparms.gssapi_delegation
 BuildRequires:  xmlrpc-c-devel >= 1.27.4
@@ -195,7 +196,7 @@ BuildRequires:  jansson-devel
 BuildRequires:  popt-devel
 BuildRequires:  gcc
 BuildRequires:  make
-BuildRequires:  pkgconfig
+BuildRequires:  pkgconf
 BuildRequires:  autoconf
 BuildRequires:  automake
 BuildRequires:  libtool