cmd/go: skip TestCgoPkgConfig if pkg-config is too old
cmd/go: skip TestCgoPkgConfig if pkg-config is too old

pkg-config 0.24 adds support for quoting and escaping whitespace;
distros like CentOS 6 are still shipping pkg-config 0.23. Skip the test
there since there's no way to get whitespace into the pkg-config output.

Fixes #17846.

Change-Id: Ie4ea17e9b709372a20178b539498929754bcd51f
Reviewed-on: https://go-review.googlesource.com/33027
Run-TryBot: Quentin Smith <d6b8e48afb2534b213e391cab43016505747a234@golang.org>
TryBot-Result: Gobot Gobot <66cb808b70d30c07676d5e946fee83fd561249e5@golang.org>
Reviewed-by: Russ Cox <5ad239cb8a44f659eaaee0aa1ea5b94947abe557@golang.org>

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