happy: drop from the bundle — 2.x needs a recipe change, not a version bump

Reverts happy to 1.20.1.1 so the other five members can land. The 2.1.6 bump
fails to build on BOTH arches:

    Error: Setup: Encountered missing or private dependencies:
    happy-lib ==2.1.6

(The `libtinfo.so.6: no version information available` lines above it in the
log are benign GHC noise, not the failure.)

happy 2.x split its library out into a separate Hackage package. `happy.cabal`
now declares `build-depends: ... happy-lib == 2.1.6`, and `happy-lib-2.1.6` is
its own tarball. Our build.sh is a bare `ghc --make Setup.hs` +
`./Setup configure/build` with no dependency resolution at all — self-contained
1.20.x builds fine that way, 2.x cannot.

So this is not a stale pin or a bad sha: the recipe's build model no longer
matches upstream's topology. A version check cannot see that; only a build can,
which is what caught it.

Fixing it means adding happy-lib as a second Source and building lib -> exe.
There's no precedent to copy — `alex` and `happy` are our only Hackage packages
and both have exactly one source — so it deserves its own PR rather than riding
an automated bundle.

Author: bryan-minimal

packages/happy/build.ncl

@@ -5,15 +5,15 @@ let ghc-bootstrap = import "../ghc-bootstrap/build.ncl" in
 let gmp = import "../gmp/build.ncl" in
 let toolchain = import "../toolchain/build.ncl" in
 
-let version = "2.1.6" in
+let version = "1.20.1.1" in
 {
   name = "happy",
 
   build_deps = [
     { file = "build.sh" } | Local,
     {
       url = "https://hackage.haskell.org/package/happy-%{version}/happy-%{version}.tar.gz",
-      sha256 = "9b473961010cb5673510f4133d914b9d5ad667b16aafe4a5555d9962dbf05b19",
+      sha256 = "8b4e7dc5a6c5fd666f8f7163232931ab28746d0d17da8fa1cbd68be9e878881b",
       extract = true,
     } | Source,
     base,