runtime: skip GDB tests on NetBSD
runtime: skip GDB tests on NetBSD

TestGdbAutotmpTypes times out for unknown reasons on NetBSd. Skip the
gdb tests on NetBSD for now.

Updates #22893

Change-Id: Ibb05b7260eabb74d805d374b25a43770939fa5f2
Reviewed-on: https://go-review.googlesource.com/80136
Run-TryBot: Ian Lance Taylor <87e9c6d529889242b7e184afb632328636553ab4@golang.org>
Reviewed-by: Brad Fitzpatrick <ae9783c0b0efc69cd85ab025ddd17aa44cdc4aa5@golang.org>
TryBot-Result: Gobot Gobot <66cb808b70d30c07676d5e946fee83fd561249e5@golang.org>

cloudflare/go,Cofyc/go,nawawi/go,akutz/go,Cofyc/go,christopher-henderson/Go,codestation/go,nawawi/go,nawawi/go,golang/go,Cofyc/go,cloudflare/go,cloudflare/go,josharian/go,CAFxX/go,cloudflare/go,CAFxX/go,golang/go,Cofyc/go,nawawi/go,CAFxX/go,Cofyc/go,codestation/go,akutz/go,CAFxX/go,josharian/go,josharian/go,akutz/go,codestation/go,codestation/go,josharian/go,Cofyc/go,golang/go,Cofyc/go,akutz/go,Cofyc/go,josharian/go,josharian/go,CAFxX/go,nawawi/go,CAFxX/go,codestation/go,cloudflare/go,golang/go,josharian/go,golang/go,codestation/go,cloudflare/go,nawawi/go,akutz/go,akutz/go,codestation/go,golang/go,cloudflare/go,CAFxX/go,akutz/go,akutz/go,golang/go,josharian/go,golang/go,cloudflare/go,nawawi/go,codestation/go,CAFxX/go,nawawi/go