cmd/link: fix glink resolver generation on ppc64le

AddSymRef grows the section to fit the relocation. This was not
being accounted for. Instead, add a relocation and explicitly
populate it so we patch the desired instructions.

Change-Id: I583147e2545aea34c854f9d35ca920c57be60b90
Reviewed-on: https://go-review.googlesource.com/c/go/+/300949
Run-TryBot: Paul Murphy <[email protected]>
Run-TryBot: Lynn Boger <[email protected]>
Reviewed-by: Cherry Zhang <[email protected]>
TryBot-Result: Go Bot <[email protected]>
Trust: Lynn Boger <[email protected]>

Author: pmur

src/cmd/link/internal/ppc64/asm.go

@@ -1039,8 +1039,11 @@ func ensureglinkresolver(ctxt *ld.Link, ldr *loader.Loader) *loader.SymbolBuilde
 	glink.AddUint32(ctxt.Arch, 0x7800f082) // srdi r0,r0,2
 
 	// r11 = address of the first byte of the PLT
-	glink.AddSymRef(ctxt.Arch, ctxt.PLT, 0, objabi.R_ADDRPOWER, 8)
-
+	r, _ := glink.AddRel(objabi.R_ADDRPOWER)
+	r.SetSym(ctxt.PLT)
+	r.SetSiz(8)
+	r.SetOff(int32(glink.Size()))
+	r.SetAdd(0)
 	glink.AddUint32(ctxt.Arch, 0x3d600000) // addis r11,0,.plt@ha
 	glink.AddUint32(ctxt.Arch, 0x396b0000) // addi r11,r11,.plt@l