test: skip rangegen.go on 32-bit platforms

Add a skip for this test that effectively disables it for 32-bit platforms,
so as to not run into timeouts or OOMs on smaller machines.

Fixes #64789.

Change-Id: I2d428e1dccae62b8bb1a69c5f95699692a282bbb
Reviewed-on: https://go-review.googlesource.com/c/go/+/550975
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Carlos Amedee <carlos@golang.org>

test/rangegen.go

@@ -25,6 +25,7 @@ import (
 	"bytes"
 	"fmt"
 	"log"
+	"math/bits"
 	"os"
 	"os/exec"
 	"strings"
@@ -37,6 +38,13 @@ func main() {
 	log.SetFlags(0)
 	log.SetPrefix("rangegen: ")
 
+	if !long && bits.UintSize == 32 {
+		// Skip this test on 32-bit platforms, where it seems to
+		// cause timeouts and build problems.
+		skip()
+		return
+	}
+
 	b := new(bytes.Buffer)
 	tests := ""
 	flush := func(force bool) {
@@ -331,3 +339,12 @@ func run(f func(*output, int)int, i int) *output {
 }
 
 `
+
+func skip() {
+	const code = `
+package main
+func main() {
+}
+`
+	fmt.Printf("%s\n", code)
+}