cmd/cgo: add more architectures to size maps

This brings over the architectures that the gofrontend knows about.
This permits using the main cgo tool for those architectures,
as cgo can be used with -godefs without gc support.
This will help add golang.org/x/sys/unix support for other architectures.

For #37443

Change-Id: I63632b9c5139e71b9ccab8edcc7acdb464229b74
Reviewed-on: https://go-review.googlesource.com/c/go/+/260657
Trust: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Than McIntosh <thanm@google.com>

src/cmd/cgo/main.go

@@ -170,35 +170,51 @@ func usage() {
 
 var ptrSizeMap = map[string]int64{
 	"386":      4,
+	"alpha":    8,
 	"amd64":    8,
 	"arm":      4,
 	"arm64":    8,
+	"m68k":     4,
 	"mips":     4,
 	"mipsle":   4,
 	"mips64":   8,
 	"mips64le": 8,
+	"nios2":    4,
+	"ppc":      4,
 	"ppc64":    8,
 	"ppc64le":  8,
+	"riscv":    4,
 	"riscv64":  8,
 	"s390":     4,
 	"s390x":    8,
+	"sh":       4,
+	"shbe":     4,
+	"sparc":    4,
 	"sparc64":  8,
 }
 
 var intSizeMap = map[string]int64{
 	"386":      4,
+	"alpha":    8,
 	"amd64":    8,
 	"arm":      4,
 	"arm64":    8,
+	"m68k":     4,
 	"mips":     4,
 	"mipsle":   4,
 	"mips64":   8,
 	"mips64le": 8,
+	"nios2":    4,
+	"ppc":      4,
 	"ppc64":    8,
 	"ppc64le":  8,
+	"riscv":    4,
 	"riscv64":  8,
 	"s390":     4,
 	"s390x":    8,
+	"sh":       4,
+	"shbe":     4,
+	"sparc":    4,
 	"sparc64":  8,
 }