erlang: fix nix-env version confusion

pkgs/development/interpreters/erlang/generic-builder.nix

@@ -84,9 +84,13 @@ let
 
 in
 stdenv.mkDerivation ({
-  name = "${baseName}-${version}"
-    + optionalString javacSupport "-javac"
-    + optionalString odbcSupport "-odbc";
+  # name is used instead of pname to
+  # - not have to pass pnames as argument
+  # - have a separate pname for erlang (main module)
+  name = "${baseName}"
+    + optionalString javacSupport "_javac"
+    + optionalString odbcSupport "_odbc"
+    + "-${version}";
 
   inherit src version;