net-snmp: import Debian patch to fix link error

pkgs/by-name/ne/net-snmp/link-error.patch

@@ -0,0 +1,17 @@
+Description: Add libnetsnmpaget link to libnetsnmptrapd
+ Causes a linking issue otherwise 
+Author: Craig Small <csmall@debian.org>
+Reviewed-by: Craig Small <csmall@debian.org>
+Last-Update: 2023-08-19
+---
+--- a/apps/Makefile.in
++++ b/apps/Makefile.in
+@@ -237,7 +237,7 @@
+ 	$(LINK) ${CFLAGS} -o $@ snmppcap.$(OSUFFIX) ${LDFLAGS} ${USEAGENTLIBS} ${LIBS} -lpcap
+ 
+ libnetsnmptrapd.$(LIB_EXTENSION)$(LIB_VERSION): $(LLIBTRAPD_OBJS)
+-	$(LIB_LD_CMD) $@ ${LLIBTRAPD_OBJS} $(MIBLIB) $(MYSQL_LIBS) $(USELIBS) $(PERLLDOPTS_FOR_LIBS) $(LDFLAGS)
++	$(LIB_LD_CMD) $@ ${LLIBTRAPD_OBJS} $(MIBLIB) $(MYSQL_LIBS) $(USELIBS) $(USEAGENTLIBS) $(PERLLDOPTS_FOR_LIBS) $(LDFLAGS)
+ 	$(RANLIB) $@
+ 
+ snmpinforminstall:

pkgs/by-name/ne/net-snmp/package.nix

@@ -29,6 +29,11 @@ stdenv.mkDerivation (finalAttrs: {
     hash = "sha256-FnB3GfgzGEpLcoNdrDWa4YgSOwa15CgXwAeQ19wThL8=";
   };
 
+  patches = [
+    # https://salsa.debian.org/debian/net-snmp/-/blob/master/debian/patches/makefile_trap_needs_agent, vendored because of Anubis
+    ./link-error.patch
+  ];
+
   outputs = [
     "bin"
     "out"