runtime: ignore rt_sigaction error if it is for SIGRTMAX
runtime: ignore rt_sigaction error if it is for SIGRTMAX

A forward port of https://codereview.appspot.com/124900043/ which somehow
got lost somewhere.

Fixes #13024

Change-Id: Iab128899e65c51d90f6704e3e1b2fc9326e3a1c2
Reviewed-on: https://go-review.googlesource.com/16853
Reviewed-by: Russ Cox <5ad239cb8a44f659eaaee0aa1ea5b94947abe557@golang.org>

nawawi/go,CAFxX/go,josharian/go,golang/go,deft-code/go,cyberroadie/go,Cofyc/go,goodlang/good,josharian/go,deft-code/go,codestation/go,miolini/go,4ad/go,theif519/go,miolini/go,cloudflare/go,josharian/go,4ad/go,rachtsingh/gogojuice,Endika/go,mwhudson/go,josharian/go,cloudflare/go,binarycrusader/go,linux-on-ibm-z/go,deft-code/go,polyverse-security/go,vsekhar/elastic-go,fjballest/golang,Samurais/go,golang/go,cloudflare/go,Endika/go,binarycrusader/go,kim-racktop/go,Endika/go,binarycrusader/go,vsekhar/elastic-go,codestation/go,golang/go,momchil-velikov/go,ganboing/go-esx,Samurais/go,ganboing/go-esx,linux-on-ibm-z/go,vanloswang/go,mwhudson/go,Jordanzuo/go,Jordanzuo/go,suncycheng/go,akutz/go,vsekhar/elastic-go,rachtsingh/gogojuice,suncycheng/go,sndnvaps/go,sndnvaps/go,mwhudson/go,ImJasonH/go,odeke-em/go,fjballest/golang,theif519/go,josharian/go,kim-racktop/go,momchil-velikov/go,nawawi/go,binarycrusader/go,vanloswang/go,cloudflare/go,rachtsingh/gogojuice,odeke-em/go,deft-code/go,polyverse-security/go,ImJasonH/go,ganboing/go-esx,akutz/go,Cofyc/go,codestation/go,cloudflare/go,mwhudson/go,codestation/go,goodlang/good,Cofyc/go,roth1002/go,Cofyc/go,linux-on-ibm-z/go,goodlang/good,roth1002/go,kim-racktop/go,4ad/go,theif519/go,cyberroadie/go,josharian/go,4ad/go,polyverse-security/go,goodlang/good,fjballest/golang,vanloswang/go,Endika/go,nawawi/go,polyverse-security/go,theif519/go,Samurais/go,ImJasonH/go,goodlang/good,derekmarcotte/go,rachtsingh/gogojuice,ImJasonH/go,kim-racktop/go,Jordanzuo/go,roth1002/go,akutz/go,derekmarcotte/go,fjballest/golang,theif519/go,odeke-em/go,fjballest/golang,mwhudson/go,odeke-em/go,rachtsingh/gogojuice,miolini/go,suncycheng/go,vsekhar/elastic-go,cyberroadie/go,codestation/go,polyverse-security/go,Cofyc/go,Jordanzuo/go,CAFxX/go,binarycrusader/go,vsekhar/elastic-go,linux-on-ibm-z/go,Samurais/go,derekmarcotte/go,sndnvaps/go,ganboing/go-esx,rachtsingh/gogojuice,golang/go,nawawi/go,suncycheng/go,linux-on-ibm-z/go,vanloswang/go,Cofyc/go,CAFxX/go,roth1002/go,deft-code/go,derekmarcotte/go,nawawi/go,momchil-velikov/go,momchil-velikov/go,sndnvaps/go,odeke-em/go,ImJasonH/go,theif519/go,Cofyc/go,akutz/go,mwhudson/go,kim-racktop/go,CAFxX/go,kim-racktop/go,rachtsingh/gogojuice,akutz/go,Endika/go,fjballest/golang,polyverse-security/go,fjballest/golang,cyberroadie/go,vsekhar/elastic-go,rachtsingh/gogojuice,suncycheng/go,vsekhar/elastic-go,kim-racktop/go,Endika/go,miolini/go,cyberroadie/go,mwhudson/go,christopher-henderson/Go,mwhudson/go,Samurais/go,cyberroadie/go,kim-racktop/go,CAFxX/go,sndnvaps/go,linux-on-ibm-z/go,sndnvaps/go,odeke-em/go,Cofyc/go,Jordanzuo/go,theif519/go,ImJasonH/go,CAFxX/go,ImJasonH/go,binarycrusader/go,theif519/go,goodlang/good,odeke-em/go,codestation/go,roth1002/go,cyberroadie/go,akutz/go,akutz/go,vsekhar/elastic-go,roth1002/go,josharian/go,momchil-velikov/go,suncycheng/go,nawawi/go,cloudflare/go,nawawi/go,fjballest/golang,codestation/go,cloudflare/go,nawawi/go,vanloswang/go,sndnvaps/go,goodlang/good,deft-code/go,suncycheng/go,Samurais/go,suncycheng/go,cyberroadie/go,momchil-velikov/go,momchil-velikov/go,deft-code/go,4ad/go,Jordanzuo/go,miolini/go,derekmarcotte/go,CAFxX/go,Samurais/go,golang/go,golang/go,binarycrusader/go,ganboing/go-esx,derekmarcotte/go,4ad/go,CAFxX/go,ganboing/go-esx,odeke-em/go,akutz/go,josharian/go,Endika/go,linux-on-ibm-z/go,roth1002/go,Jordanzuo/go,deft-code/go,sndnvaps/go,polyverse-security/go,miolini/go,vanloswang/go,derekmarcotte/go,golang/go,roth1002/go,ImJasonH/go,vanloswang/go,Jordanzuo/go,polyverse-security/go,4ad/go,golang/go,ganboing/go-esx,miolini/go,derekmarcotte/go,4ad/go,codestation/go,momchil-velikov/go,Endika/go,vanloswang/go,cloudflare/go,goodlang/good,binarycrusader/go,linux-on-ibm-z/go,Samurais/go,miolini/go,ganboing/go-esx