(PA-5998) Add sles11-x86_64 to puppet-runtime

[amitkarsale]

Enforcing runtime build to use latest gcc i.e pl-gcc8

[joshcooper]

Since this platform definition is shared by both agent-runtime-7.x and agent-runtime-main, I'm thinking it would be better to install pl-gcc8 in

puppet-runtime/configs/components/runtime-agent.rb

Lines 6 to 10 in 531fb1f

	if platform.name =~ /sles-11-x86_64/ && settings[:ruby_version] =~ /2.7/
	pkg.install do
	"zypper install -y --oldpackage pl-gcc=4.8.2-1"
	end
	end

so that we don't install pl-gcc8 for 7.x and then downgrade to an older version. Also keeping both gcc versions in the same place is a plus