[libvirt] [PATCH] build: improve rpm generation for distro backports

[Eric Blake]

When building for an older distro, it's convenient to just
tell rpmbuild to define dist (for example, to .el6_0), rather
than also remembering to define rhel to 6.

* libvirt.spec.in: Guess %{rhel} based on %{dist}.
Based on an idea by Jiri Denemark.
---

In patch form:

 libvirt.spec.in |    8 ++++++++
 1 files changed, 8 insertions(+), 0 deletions(-)

diff --git a/libvirt.spec.in b/libvirt.spec.in
index 45a8fe0..1946a15 100644
--- a/libvirt.spec.in
+++ b/libvirt.spec.in
@@ -1,5 +1,13 @@
 # -*- rpm-spec -*-

+# If neither fedora nor rhel was defined, try to guess them from %{dist}
+%if !0%{?rhel} && !0%{?fedora}
+%{expand:%(echo "%{?dist}" | \
+  sed -ne 's/^\.el\([0-9]\+\).*/%%define rhel \1/p')}
+%{expand:%(echo "%{?dist}" | \
+  sed -ne 's/^\.fc\?\([0-9]\+\).*/%%define fedora \1/p')}
+%endif
+
 # A client only build will create a libvirt.so only containing
 # the generic RPC driver, and test driver and no libvirtd
 # Default to a full server + client build
-- 
1.7.4