cmd/link: align .reloc block starts by 32 bits for PE target
Tweak the code that emits the PE ".reloc" section on Windows to ensure
that each relocation block is 32-bit aligned, which is required by the
PE standard.
Fixes #68260.
Change-Id: I39b75a7491b00fa97871aebb90d3be0ec09f9c40
Reviewed-on: https://go-review.googlesource.com/c/go/+/595896 Reviewed-by: Cherry Mui <cherryyz@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>