cmd/link: ignore macho symbols in invalid sections
cmd/link: ignore macho symbols in invalid sections

Restores linker behavior that existed before CL 68930.
Hopefully fixes the macOS 10.8 builder.

Change-Id: Ib8d6923b59543008cf71c4625addb4e2045cedf6
Reviewed-on: https://go-review.googlesource.com/69170
Run-TryBot: David Crawshaw <a2f0bf29257797dd66800b4fbb9945c3e216c004@golang.org>
TryBot-Result: Gobot Gobot <66cb808b70d30c07676d5e946fee83fd561249e5@golang.org>
Reviewed-by: Ian Lance Taylor <87e9c6d529889242b7e184afb632328636553ab4@golang.org>
Reviewed-by: Marvin Stenger <bde3f4ccdd7c08fc2bda30f654959132eeced9b3@gmail.com>

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