cmd/dist, cmd/go: move CGO_ENABLED from 'go tool dist env' to 'go env'

So that we don't duplicate knowledge about which OS/ARCH combination
        supports cgo.
        Also updated src/run.bash and src/sudo.bash to use 'go env'.

R=golang-dev, rsc
CC=golang-dev
https://golang.org/cl/5792055

src/cmd/dist/build.c

@@ -52,19 +52,6 @@ static char *okgoos[] = {
 	"windows",
 };
 
-// The known cgo-enabled combinations.
-// This list is also known to ../../pkg/go/build/build.go.
-static char *okcgo[] = {
-	"darwin/386",
-	"darwin/amd64",
-	"linux/386",
-	"linux/amd64",
-	"freebsd/386",
-	"freebsd/amd64",
-	"windows/386",
-	"windows/amd64",
-};
-
 static void rmworkdir(void);
 
 // find reports the first index of p in l[0:n], or else -1.
@@ -1321,11 +1308,6 @@ cmdenv(int argc, char **argv)
 	xprintf(format, "GOTOOLDIR", tooldir);
 	xprintf(format, "GOCHAR", gochar);
 
-	if(find(bprintf(&b, "%s/%s", goos, goarch), okcgo, nelem(okcgo)) >= 0)
-		xprintf(format, "CGO_ENABLED", "1");
-	else
-		xprintf(format, "CGO_ENABLED", "0");
-
 	if(pflag) {
 		sep = ":";
 		if(streq(gohostos, "windows"))

src/cmd/go/env.go

@@ -45,6 +45,12 @@ func mkEnv() []envVar {
 		{"GOGCCFLAGS", strings.Join(b.gccCmd(".")[3:], " ")},
 	}
 
+	if buildContext.CgoEnabled {
+		env = append(env, envVar{"CGO_ENABLED", "1"})
+	} else {
+		env = append(env, envVar{"CGO_ENABLED", "0"})
+	}
+
 	return env
 }
 

src/run.bash

@@ -5,7 +5,7 @@
 
 set -e
 
-eval $(go tool dist env)
+eval $(go env)
 
 unset CDPATH	# in case user has it set
 

src/sudo.bash

@@ -17,7 +17,7 @@ if [[ ! -d /usr/local/bin ]]; then
 	exit 2
 fi
 
-eval $(go tool dist env)
+eval $(go env)
 cd $(dirname $0)
 for i in prof cov
 do