cmd/cgo/internal/swig,cmd/go: reenable swig tests on 386

CL 588938 skipped the tests because they were broken to unblock the
builders, but we're fairly certain the reason they were failing is
because we're missing g++-multilib. This change is intended to land once
CL 589175 is deployed.

Fixes #67698.

Change-Id: I5bb679290ae9ba9ab3bda9499cdf1eec649bc066
Reviewed-on: https://go-review.googlesource.com/c/go/+/589195
Reviewed-by: Ian Lance Taylor <iant@google.com>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Auto-Submit: Michael Knyszek <mknyszek@google.com>
Reviewed-by: Dmitri Shuralyov <dmitshur@golang.org>

src/cmd/cgo/internal/swig/swig_test.go

@@ -11,7 +11,6 @@ import (
 	"os/exec"
 	"path/filepath"
 	"regexp"
-	"runtime"
 	"strconv"
 	"strings"
 	"sync"
@@ -74,13 +73,6 @@ func mustHaveCxx(t *testing.T) {
 		t.Skip("no C++ compiler")
 	}
 	testenv.MustHaveExecPath(t, string(args[0]))
-
-	// On the builders, the C++ toolchain doesn't quite work for these tests
-	// for 386 builders or on the clang builders. Thing is, these tests historically
-	// didn't even run on these builders *at all*, so just skip. See #67698.
-	if builder := testenv.Builder(); builder != "" && runtime.GOARCH == "386" {
-		t.Skip("test skipped on 386 on builders because of incompatibility with the C++ toolchain available on builders; see go.dev/issue/67698")
-	}
 }
 
 var (

src/cmd/go/testdata/script/list_swigcxx.txt

@@ -4,9 +4,6 @@
 [!exec:g++] skip
 [!cgo] skip
 
-# See go.dev/issue/67698.
-[GOARCH:386] skip
-
 # CompiledGoFiles should contain 4 files:
 #  a.go
 #  _cgo_import.go [gc only]