lammps: add mpich to nativeBuildInputs if needed

Before `strictDeps` was enabled in
b2d648ff9b, the `MPIIO` package could have
worked with `mpich` added to `buildInputs`. However this was wrong and
made the compilation fail (with `MPIIO = true;` set by user override in
`packages` attribute set). To make it easier for users who want to
include MPI support in lammps, we take care of adding `mpich` by
ourselves.

pkgs/by-name/la/lammps/package.nix

@@ -8,6 +8,7 @@
   blas,
   lapack,
   python3,
+  mpich,
   cmake,
   autoAddDriverRunpath,
   pkg-config,
@@ -39,6 +40,7 @@
     SRD = true;
     REAXFF = true;
     PYTHON = true;
+    MPIIO = true;
   },
   # Extra cmakeFlags to add as "-D${attr}=${value}"
   extraCmakeFlags ? { },
@@ -73,6 +75,9 @@ stdenv.mkDerivation (finalAttrs: {
   ]
   ++ lib.optionals packages.PYTHON [
     python3
+  ]
+  ++ lib.optionals packages.MPIIO [
+    mpich
   ];
 
   passthru = {