redhat: Fix dependencies for rpm package

- Add bison, flex & autoconf
- Remove systemd for systems without it (i.e. CentOS 6)
- Update doc to reflect dependencies

Signed-off-by: Martin Winter <mwinter@opensourcerouting.org>

redhat/README.rpm_build.md

@@ -6,10 +6,18 @@ Building your own FRRouting RPM
 
         yum install git autoconf automake libtool make gawk readline-devel \
         texinfo dejagnu net-snmp-devel groff rpm-build net-snmp-devel \
-        libcap-devel texi2html
+        libcap-devel texi2html bison flex
+
+    Additionally, on systems with systemd (CentOS 7, Fedora)
+
+        yum install systemd-devel
 
     (use `dnf install` on new Fedora instead of `yum install`)
-    
+
+    **CentOS 6:** Please check doc/Building_FRR_on_CentOS6.md for details on
+    how to install required version of autoconf, automake and bison. The
+    versions in the common Repo are too old.
+
 2. Checkout FRR under a **unpriviledged** user account
 
         git clone https://github.com/frrouting/frr.git frr

redhat/frr.spec.in

@@ -113,16 +113,16 @@ Requires:       ncurses json-c
 Requires(pre):  /sbin/install-info
 Requires(preun): /sbin/install-info
 Requires(post): /sbin/install-info
-BuildRequires:  texi2html texinfo autoconf patch libcap-devel groff 
+BuildRequires:  texi2html texinfo autoconf automake patch libcap-devel groff
 BuildRequires:  readline readline-devel ncurses ncurses-devel
-BuildRequires:  json-c-devel bison flex
+BuildRequires:  json-c-devel bison >= 2.7 flex
 Requires:       ncurses initscripts
 %if %{with_pam}
 BuildRequires:  pam-devel
 Requires:       pam
 %endif
 %if "%{initsystem}" == "systemd"
-BuildRequires:      systemd
+BuildRequires:      systemd systemd-devel
 Requires(post):     systemd
 Requires(preun):    systemd
 Requires(postun):   systemd
@@ -254,7 +254,9 @@ developing OSPF-API and frr applications.
 %endif
     --enable-gcc-rdynamic \
     --enable-isisd=yes \
+%if "%{initsystem}" == "systemd"
     --enable-systemd=yes \
+%endif
     --enable-poll=yes
 
 make %{?_smp_mflags} MAKEINFO="makeinfo --no-split"