[rpm] use rpm macros to identify build distro

thanks Honza for spotting it

Signed-off-by: Fabio M. Di Nitto <fdinitto@redhat.com>
Reviewed-by: Jan Friesse <jfriesse@redhat.com>

corosync.spec.in

@@ -32,15 +32,17 @@ Requires: corosynclib%{?_isa} = %{version}-%{release}
 
 # Build bits
 
-# OpenSUSE needs groff-full to build html documentation,
-# but there is no clean way to express it here.
+%if 0%{?suse_version}
+BuildRequires: groff-full
+%else
 BuildRequires: groff
+%endif
 BuildRequires: libqb-devel
-# Use file based depedency to allow upstream spec file to
-# build on OpenSUSE since package name differs with Fedora/RHEL/Centos
-# and only recent versions of rpm supports BuildRequires: foo || bar
-# BuildRequires: nss-devel || mozilla-nss-devel
-BuildRequires: /usr/include/nss3/nss.h /usr/include/nspr4/nspr.h
+%if 0%{?suse_version}
+BuildRequires: mozilla-nss-devel
+%else
+BuildRequires: nss-devel
+%endif
 BuildRequires: libknet1-devel
 BuildRequires: zlib-devel
 %if %{with runautogen}
@@ -53,11 +55,11 @@ BuildRequires: libstatgrab-devel
 BuildRequires: net-snmp-devel
 %endif
 %if %{with dbus}
-# Use file based depedency to allow upstream spec file to
-# build on OpenSUSE since package name differs with Fedora/RHEL/Centos
-# and only recent versions of rpm supports BuildRequires: foo || bar
-# BuildRequires: dbus-devel || dbus-1-devel
-BuildRequires: /usr/include/dbus-1.0/dbus/dbus.h
+%if 0%{?suse_version}
+BuildRequires: dbus-1-devel
+%else
+BuildRequires: dbus-devel
+%endif
 %endif
 %if %{with systemd}
 %{?systemd_requires}