cmd/compile: prefer base.Fatalf to panic in dwarfgen

Updates a few spots which call `panic` to instead call `base.Fatalf`.

Change-Id: I30b73c7994caa647245b0e253f20e0b88185e644
GitHub-Last-Rev: b3839bb
GitHub-Pull-Request: #74616
Reviewed-on: https://go-review.googlesource.com/c/go/+/688035
Reviewed-by: Keith Randall <khr@golang.org>
Reviewed-by: Michael Knyszek <mknyszek@google.com>
Reviewed-by: Keith Randall <khr@google.com>
Auto-Submit: Michael Knyszek <mknyszek@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>

Author: derekparker

src/cmd/compile/internal/dwarfgen/dwarf.go

@@ -203,7 +203,7 @@ func createDwarfVars(fnsym *obj.LSym, complexOK bool, fn *ir.Func, apDecls []*ir
 				continue
 			}
 			if n.Class != ir.PPARAMOUT || !n.IsOutputParamInRegisters() {
-				panic("invalid ir.Name on debugInfo.RegOutputParams list")
+				base.Fatalf("invalid ir.Name on debugInfo.RegOutputParams list")
 			}
 			dcl = append(dcl, n)
 		}
@@ -583,7 +583,7 @@ func createHeapDerefLocationList(n *ir.Name, entryID ssa.ID) []byte {
 // in the DWARF info.
 func RecordFlags(flags ...string) {
 	if base.Ctxt.Pkgpath == "" {
-		panic("missing pkgpath")
+		base.Fatalf("missing pkgpath")
 	}
 
 	type BoolFlag interface {