Add missing BuildRequires on gcc

configure: error: no acceptable C compiler found in $PATH

References: https://bugzilla.redhat.com/show_bug.cgi?id=1604555
Signed-off-by: Igor Gnatenko <ignatenkobrain@fedoraproject.org>

libbsd.spec

@@ -9,6 +9,7 @@ Source0:        http://libbsd.freedesktop.org/releases/libbsd-%{version}.tar.xz
 Patch1:         %{name}-0.8.3-deprecated.patch
 Patch2:         %{name}-0.8.6-compat.patch
 
+BuildRequires:  gcc
 %description
 libbsd provides useful functions commonly found on BSD systems, and
 lacking on others like GNU systems, thus making it easier to port