cmd/dist, go/build: add power64, power64le to known GOARCH lists

LGTM=dave, minux, aram
R=minux, dave, bradfitz, aram
CC=golang-codereviews
https://golang.org/cl/119470043

src/cmd/dist/build.c

@@ -40,7 +40,7 @@ static void dopack(char*, char*, char**, int);
 static char *findgoversion(void);
 
 // The known architecture letters.
-static char *gochars = "5668";
+static char *gochars = "566899";
 
 // The known architectures.
 static char *okgoarch[] = {
@@ -49,6 +49,8 @@ static char *okgoarch[] = {
 	"amd64",
 	"amd64p32",
 	"386",
+	"power64",
+	"power64le",
 };
 
 // The known operating systems.

src/pkg/go/build/build.go

@@ -1230,6 +1230,8 @@ func ArchChar(goarch string) (string, error) {
 		return "6", nil
 	case "arm":
 		return "5", nil
+	case "power64", "power64le":
+		return "9", nil
 	}
 	return "", errors.New("unsupported GOARCH " + goarch)
 }

src/pkg/go/build/syslist.go

@@ -5,4 +5,4 @@
 package build
 
 const goosList = "android darwin dragonfly freebsd linux nacl netbsd openbsd plan9 solaris windows "
-const goarchList = "386 amd64 amd64p32 arm "
+const goarchList = "386 amd64 amd64p32 arm power64 power64le "