[vpython] Fix PEP425 naming.

vpython/cipd/pep425.go

 // Copyright 2017 The LUCI Authors. All rights reserved.
 // Use of this source code is governed under the Apache License, Version 2.0
 // that can be found in the LICENSE file.
 
 package cipd
 
 import (
         "strings"
 
         "github.com/luci/luci-go/vpython/api/vpython"
 )
 
 // PlatformForPEP425Tag returns the CIPD platform inferred from a given Python
 // PEP425 tag.
 //
-// If the platform could not be determined, an empoty string will be returned.
-func PlatformForPEP425Tag(t *vpython.Pep425Tag) string {
-        switch archSplit := strings.SplitN(t.Arch, "_", 2); archSplit[0] {
+// If the platform could not be determined, an empty string will be returned.
+func PlatformForPEP425Tag(t *vpython.PEP425Tag) string {
+        switch platSplit := strings.SplitN(t.Platform, "_", 2); platSplit[0] {
         case "linux", "manylinux1":
                 // Grab the remainder.
                 //
                 // Examples:
                 // - linux_i686
                 // - manylinux1_x86_64
                 // - linux_arm64
                 cpu := ""
-                if len(archSplit) > 1 {
-                        cpu = archSplit[1]
+                if len(platSplit) > 1 {
+                        cpu = platSplit[1]
                 }
                 switch cpu {
                 case "i686":
                         return "linux-386"
                 case "x86_64":
                         return "linux-amd64"
                 case "arm64":
                         return "linux-arm64"
                 case "mipsel", "mips":
                         return "linux-mips32"
                 case "mips64":
                         return "linux-mips64"
                 default:
                         // All remaining "arm*" get the "armv6l" CIPD platform.
                         if strings.HasPrefix(cpu, "arm") {
                                 return "linux-armv6l"
                         }
                         return ""
                 }
 
         case "macosx":
                 // Grab the last token.
                 //
                 // Examples:
                 // - macosx_10_10_intel
                 // - macosx_10_10_i386
-                if len(archSplit) == 1 {
+                if len(platSplit) == 1 {
                         return ""
                 }
-                suffixSplit := strings.SplitN(archSplit[1], "_", -1)
+                suffixSplit := strings.SplitN(platSplit[1], "_", -1)
                 switch suffixSplit[len(suffixSplit)-1] {
                 case "intel", "x86_64", "fat64", "universal":
                         return "mac-amd64"
                 case "i386", "fat32":
                         return "mac-386"
                 default:
                         return ""
                 }
 
         case "win32":
                 // win32
                 return "windows-386"
         case "win":
                 // Examples:
                 // - win_amd64
-                if len(archSplit) == 1 {
+                if len(platSplit) == 1 {
                         return ""
                 }
-                switch archSplit[1] {
+                switch platSplit[1] {
                 case "amd64":
                         return "windows-amd64"
                 default:
                         return ""
                 }
 
         default:
                 return ""
         }
 }