cmd/link: patch up symbols only once per object file
cmd/link: patch up symbols only once per object file

name       old s/op   new s/op   delta
LinkCmdGo  0.57 ± 5%  0.55 ± 6%  -2.37%  (p=0.000 n=97+98)

GOGC=off:

name       old s/op   new s/op   delta
LinkCmdGo  0.48 ± 3%  0.47 ± 3%  -2.90%  (p=0.000 n=100+100)

Change-Id: I1a36dbf84914cacb79842bc0ddb1e26b4c5a5828
Reviewed-on: https://go-review.googlesource.com/20917
Reviewed-by: David Crawshaw <a2f0bf29257797dd66800b4fbb9945c3e216c004@golang.org>
Run-TryBot: David Crawshaw <a2f0bf29257797dd66800b4fbb9945c3e216c004@golang.org>
TryBot-Result: Gobot Gobot <66cb808b70d30c07676d5e946fee83fd561249e5@golang.org>

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