test: print output on link -X failure
test: print output on link -X failure

(Split out from CL 22205.)

Change-Id: Iab66ac2a1cd3716966d8e59c570931bce95aba9b
Reviewed-on: https://go-review.googlesource.com/22297
Reviewed-by: Brad Fitzpatrick <ae9783c0b0efc69cd85ab025ddd17aa44cdc4aa5@golang.org>

4ad/go,derekmarcotte/go,ganboing/go-esx,codestation/go,golang/go,polyverse-security/go,linux-on-ibm-z/go,akutz/go,linux-on-ibm-z/go,vsekhar/elastic-go,theif519/go,josharian/go,cloudflare/go,ganboing/go-esx,4ad/go,CAFxX/go,ImJasonH/go,ganboing/go-esx,vsekhar/elastic-go,codestation/go,goodlang/good,4ad/go,golang/go,vsekhar/elastic-go,ganboing/go-esx,akutz/go,ImJasonH/go,golang/go,ImJasonH/go,goodlang/good,momchil-velikov/go,golang/go,vsekhar/elastic-go,polyverse-security/go,cloudflare/go,cloudflare/go,suncycheng/go,goodlang/good,josharian/go,codestation/go,cloudflare/go,suncycheng/go,christopher-henderson/Go,goodlang/good,4ad/go,akutz/go,momchil-velikov/go,codestation/go,vsekhar/elastic-go,codestation/go,suncycheng/go,4ad/go,Cofyc/go,Cofyc/go,suncycheng/go,momchil-velikov/go,cloudflare/go,Cofyc/go,momchil-velikov/go,derekmarcotte/go,ImJasonH/go,goodlang/good,CAFxX/go,derekmarcotte/go,josharian/go,goodlang/good,golang/go,momchil-velikov/go,nawawi/go,ganboing/go-esx,vsekhar/elastic-go,derekmarcotte/go,polyverse-security/go,theif519/go,nawawi/go,goodlang/good,theif519/go,akutz/go,suncycheng/go,CAFxX/go,josharian/go,ImJasonH/go,suncycheng/go,nawawi/go,CAFxX/go,cloudflare/go,ImJasonH/go,golang/go,polyverse-security/go,Cofyc/go,ImJasonH/go,codestation/go,linux-on-ibm-z/go,ganboing/go-esx,linux-on-ibm-z/go,nawawi/go,Cofyc/go,Cofyc/go,akutz/go,4ad/go,derekmarcotte/go,ImJasonH/go,Cofyc/go,vsekhar/elastic-go,theif519/go,Cofyc/go,polyverse-security/go,theif519/go,CAFxX/go,momchil-velikov/go,CAFxX/go,josharian/go,goodlang/good,ganboing/go-esx,cloudflare/go,vsekhar/elastic-go,nawawi/go,polyverse-security/go,linux-on-ibm-z/go,polyverse-security/go,josharian/go,josharian/go,akutz/go,akutz/go,derekmarcotte/go,akutz/go,ganboing/go-esx,golang/go,4ad/go,nawawi/go,codestation/go,theif519/go,suncycheng/go,linux-on-ibm-z/go,nawawi/go,momchil-velikov/go,theif519/go,CAFxX/go,CAFxX/go,golang/go,derekmarcotte/go,derekmarcotte/go,josharian/go,suncycheng/go,momchil-velikov/go,codestation/go,linux-on-ibm-z/go,theif519/go,cloudflare/go,4ad/go,nawawi/go,polyverse-security/go,linux-on-ibm-z/go