cmd/compile/internal/ssa/gen: set wasm genfile
cmd/compile/internal/ssa/gen: set wasm genfile

This appears to have been an oversight and/or
left over from development.

Setting the genfile means that extra sanity
checks are executed when regenerating SSA files.
They already pass.

Change-Id: Icc01ecf85020d3d51355e8bccfbc521b52371747
Reviewed-on: https://go-review.googlesource.com/c/154459
Run-TryBot: Josh Bleecher Snyder <cdc248cc4d32e4fbfe04e45228163bcecd48a0b9@gmail.com>
Reviewed-by: Keith Randall <8c99c3a9284e493be632950b84cd789d08ed3e9d@golang.org>

akutz/go,akutz/go,CAFxX/go,nawawi/go,cloudflare/go,akutz/go,nawawi/go,golang/go,akutz/go,josharian/go,golang/go,josharian/go,josharian/go,CAFxX/go,CAFxX/go,golang/go,golang/go,josharian/go,akutz/go,cloudflare/go,cloudflare/go,cloudflare/go,golang/go,josharian/go,nawawi/go,josharian/go,nawawi/go,cloudflare/go,CAFxX/go,CAFxX/go,nawawi/go,CAFxX/go,cloudflare/go,josharian/go,akutz/go,cloudflare/go,nawawi/go,nawawi/go,CAFxX/go,akutz/go,CAFxX/go,golang/go,akutz/go,nawawi/go,golang/go,cloudflare/go,golang/go,josharian/go