Teach cmd/dist about GOARCH=arm64

dist7.patch

diff --git a/src/cmd/dist/build.c b/src/cmd/dist/build.c
index e4b8b58..04bf6cf 100644
--- a/src/cmd/dist/build.c
+++ b/src/cmd/dist/build.c
@@ -39,7 +39,7 @@ static void dopack(char*, char*, char**, int);
 static char *findgoversion(void);
 
 // The known architecture letters.
-static char *gochars = "566899";
+static char *gochars = "5667899";
 
 // The known architectures.
 static char *okgoarch[] = {
@@ -47,6 +47,7 @@ static char *okgoarch[] = {
 	"arm",
 	"amd64",
 	"amd64p32",
+	"arm64",
 	"386",
 	"ppc64",
 	"ppc64le",
diff --git a/src/cmd/dist/buildgc.c b/src/cmd/dist/buildgc.c
index 64434d5..c0302eb 100644
--- a/src/cmd/dist/buildgc.c
+++ b/src/cmd/dist/buildgc.c
@@ -73,7 +73,7 @@ xatoi(char *s, char **end)
 	return val;
 }
 
-// mkanames reads [5689].out.h and writes anames[5689].c
+// mkanames reads [56789].out.h and writes anames[56789].c
 // The format is much the same as the Go opcodes above.
 // It also writes out cnames array for C_* constants and the dnames
 // array for D_* constants.
diff --git a/src/cmd/dist/unix.c b/src/cmd/dist/unix.c
index 0fd17c1..6b2e675 100644
--- a/src/cmd/dist/unix.c
+++ b/src/cmd/dist/unix.c
@@ -708,6 +708,8 @@ main(int argc, char **argv)
 			gohostarch = "386";
 		else if(contains(u.machine, "arm"))
 			gohostarch = "arm";
+		else if(contains(u.machine, "aarch64"))
+			gohostarch = "arm64";
 		else if(contains(u.machine, "ppc64le"))
 			gohostarch = "ppc64le";
 		else if(contains(u.machine, "ppc64"))
diff --git a/src/go/build/build.go b/src/go/build/build.go
index 12c20e5..c62425a 100644
--- a/src/go/build/build.go
+++ b/src/go/build/build.go
@@ -1386,6 +1386,8 @@ func ArchChar(goarch string) (string, error) {
 		return "6", nil
 	case "arm":
 		return "5", nil
+	case "arm64":
+		return "7", nil
 	case "ppc64", "ppc64le":
 		return "9", nil
 	}
diff --git a/src/go/build/syslist.go b/src/go/build/syslist.go
index 9246cbf..e84a066 100644
--- a/src/go/build/syslist.go
+++ b/src/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 ppc64 ppc64le "
+const goarchList = "386 amd64 amd64p32 arm arm64 ppc64 ppc64le "

Hello, thanks for posting this. I'm trying to build on iOS arm64 using Minux's goios fork. Building on armv7 (GOARCH=arm) works great, but I can't get arm64 working, even with your patch.

Any thoughts on what's going on? I'm pretty new to the Go build system / toolchain so I'm not sure what's failing or why.

##### Building compilers and Go bootstrap tool for host, darwin/amd64.
lib9
libbio
liblink
cmd/gc
cmd/6l
cmd/7l
go tool dist: opendir /Users/keith/.../goios-arm64/src/cmd/7l: No such file or directory