rpm: don't BR dhcp-client

We don't need the builder to install dhcp-client to build with support for
it. Requiring it to be installed it not great because it has runtime
implications -- it installs a dispatcher script.

https://gitlab.freedesktop.org/NetworkManager/NetworkManager/-/merge_requests/1503

contrib/fedora/rpm/NetworkManager.spec

@@ -259,7 +259,6 @@ BuildRequires: gnutls-devel >= 2.12
 %else
 BuildRequires: nss-devel >= 3.11.7
 %endif
-BuildRequires: dhclient
 BuildRequires: readline-devel
 BuildRequires: audit-libs-devel
 %if %{with regen_docs}
@@ -614,8 +613,9 @@ Preferably use nmcli instead.
 %if %{with test}
 	--werror \
 %endif
-	-Dnft=/usr/sbin/nft \
-	-Diptables=/usr/sbin/iptables \
+	-Dnft=%{_sbindir}/nft \
+	-Diptables=%{_sbindir}/iptables \
+	-Ddhclient=%{_sbindir}/dhclient \
 	-Ddhcpcanon=no \
 	-Ddhcpcd=no \
 	-Dconfig_dhcp_default=%{dhcp_default} \
@@ -743,9 +743,9 @@ autoreconf --install --force
 	--with-runstatedir=%{_rundir} \
 	--enable-silent-rules=no \
 	--enable-static=no \
-	--with-nft=/usr/sbin/nft \
-	--with-iptables=/usr/sbin/iptables \
-	--with-dhclient=yes \
+	--with-nft=%{_sbindir}/nft \
+	--with-iptables=%{_sbindir}/iptables \
+	--with-dhclient=%{_sbindir}/dhclient \
 	--with-dhcpcd=no \
 	--with-dhcpcanon=no \
 	--with-config-dhcp-default=%{dhcp_default} \