cmd/compile: added test to ensure that accidental fix remains
cmd/compile: added test to ensure that accidental fix remains

Bug 15141 was apparently fixed by some other change to the
compiler (this is plausible, it was a weird bug dependent
on a particular way of returning a large named array result),
add the test to ensure that it stays fixed.

Updates #15141.

Change-Id: I3d6937556413fab1af31c5a1940e6931563ce2f3
Reviewed-on: https://go-review.googlesource.com/31972
Run-TryBot: David Chase <ae171625adc8645b8b79b7e405a6da5aba5341e0@google.com>
Reviewed-by: Brad Fitzpatrick <ae9783c0b0efc69cd85ab025ddd17aa44cdc4aa5@golang.org>
TryBot-Result: Gobot Gobot <66cb808b70d30c07676d5e946fee83fd561249e5@golang.org>

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