go/internal/gccgoimporter: test fix for older gccgo versions

Avoid running the test for issue 29198 if the available copy of gccgo
is too old (needs to support context package). Fixes a failure on the
solaris builder.

Updates #29198.

Change-Id: I2b1b3438f4ac105432f30078fbef78e24f2077cd
Reviewed-on: https://go-review.googlesource.com/c/153831
Run-TryBot: Than McIntosh <thanm@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

src/go/internal/gccgoimporter/importer_test.go

@@ -159,7 +159,7 @@ func TestObjImporter(t *testing.T) {
 
 	for _, test := range importerTests {
 		// Support for type aliases was added in GCC 7.
-		if test.pkgpath == "aliases" || test.pkgpath == "issue27856" {
+		if test.pkgpath == "aliases" || test.pkgpath == "issue27856" || test.pkgpath == "issue29198" {
 			if major < 7 {
 				t.Logf("skipping %q: not supported before gccgo version 7", test.pkgpath)
 				continue