net-snmp: drop build-only references from the closure

Before the change `net-snmp` embedded it's `./configure` options as is
and retained unneeded dependencies:

$ nix path-info -rSh $(nix-build -A net-snmp.lib) | nl |& unnix
1 /<<NIX>>/libunistring-1.1 1.8M
2 /<<NIX>>/xgcc-12.3.0-libgcc 139.1K
3 /<<NIX>>/libidn2-2.3.4 2.1M
4 /<<NIX>>/glibc-2.38-23 31.1M
5 /<<NIX>>/net-snmp-5.9.4 1.7M
6 /<<NIX>>/bash-5.2-p15 32.6M
7 /<<NIX>>/openssl-3.0.11 37.3M
8 /<<NIX>>/openssl-3.0.11-bin 39.8M
9 /<<NIX>>/openssl-3.0.11-dev 41.7M
10 /<<NIX>>/net-snmp-5.9.4-lib 46.2M

After the change the closure skips `openssl.dev` input and gets rid of
5MB of closure:

$ nix path-info -rSh $(nix-build -A net-snmp.lib) | nl |& unnix
1 /<<NIX>>/libunistring-1.1 1.8M
2 /<<NIX>>/xgcc-12.3.0-libgcc 139.1K
3 /<<NIX>>/libidn2-2.3.4 2.1M
4 /<<NIX>>/glibc-2.38-23 31.1M
5 /<<NIX>>/net-snmp-5.9.4 1.7M
6 /<<NIX>>/openssl-3.0.11 37.3M
7 /<<NIX>>/net-snmp-5.9.4-lib 41.8M

pkgs/servers/monitoring/net-snmp/default.nix

···
-{ lib, stdenv, fetchurl, fetchpatch, removeReferencesTo
+{ lib, stdenv, fetchurl, fetchpatch
 , file, openssl, perl, perlPackages, nettools
 , withPerlTools ? false }: let
 
···
     substituteInPlace testing/fulltests/support/simple_TESTCONF.sh --replace "/bin/netstat" "${nettools}/bin/netstat"
   '';
 
-  nativeBuildInputs = [ nettools removeReferencesTo file ];
+  postConfigure = ''
+    # libraries contain configure options. Mangle store paths out from
+    # ./configure-generated file.
+    sed -i include/net-snmp/net-snmp-config.h \
+      -e "/NETSNMP_CONFIGURE_OPTIONS/ s|$NIX_STORE/[a-z0-9]\{32\}-|$NIX_STORE/eeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee-|g"
+  '';
+
+  nativeBuildInputs = [ nettools file ];
   buildInputs = [ openssl ]
     ++ lib.optional withPerlTools perlWithPkgs;
 
···
     done
     mkdir $dev/bin
     mv $bin/bin/net-snmp-config $dev/bin
-    # libraries contain configure options
-    find $lib/lib -type f -exec remove-references-to -t $bin '{}' +
-    find $lib/lib -type f -exec remove-references-to -t $dev '{}' +
   '';
 
   meta = with lib; {