Re-add go:build ignore lines

This reverts commit bab2f96e2637acb107fe9b099c58befbca918748. This
clears the sea of red in my editor.

Change-Id: I600ef6c36556fb526da729f0f0d8bc69db5c5a08
Reviewed-on: https://boringssl-review.googlesource.com/c/boringssl/+/59186
Reviewed-by: Adam Langley <agl@google.com>
Commit-Queue: David Benjamin <davidben@google.com>
diff --git a/crypto/x509/test/make_invalid_extensions.go b/crypto/x509/test/make_invalid_extensions.go
index 884d933..8287bf8 100644
--- a/crypto/x509/test/make_invalid_extensions.go
+++ b/crypto/x509/test/make_invalid_extensions.go
@@ -12,6 +12,8 @@
 // OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
 // CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 
+//go:build ignore
+
 // make_invalid_extensions.go generates a number of certificate chains with
 // invalid extension encodings.
 package main