Let me amend:

in the log I see an occurrence with a comma, rather than an "and", like this

commit 3b175eab84f9899804b466506a57b5807285150a
Author: Marius Bakke <mbakke@fastmail.com>
Commit: Marius Bakke <mbakke@fastmail.com>

    gnu: nss, nss-certs: Update to 3.29.2.
    
    * gnu/packages/certs.scm (nss-certs): Update to 3.29.2.
    * gnu/packages/gnuzilla.scm (nss): Update to 3.29.2.
    * gnu/packages/patches/nss-pkgconfig.patch: Adapt to context changes.


You could probably do like this

Subject: [PATCH] gnu: Add LLVM, CLANG 3.9.1.

* gnu/packages/llvm.scm (llvm-3.9.1): New variable.
* gnu/packages/llvm.scm (clang-3.9.1): New variable.
* gnu/packages/llvm.scm (clang-runtime-3.9.1): New variable.