[6.0] 2a28faac3 vtc: Skip u12 on Alpine Linux

[Dridi Boukelmoune]

commit 2a28faac393cd77a562e74cda354159387d4b680
Author: Dridi Boukelmoune <dridi.boukelmoune at gmail.com>
Date:   Wed Jun 19 17:45:04 2024 +0200

    vtc: Skip u12 on Alpine Linux
    
    I'm not sure why this test is suddenly failing on circleci, but it used
    to pass when build jobs were running docker in docker, and it passes for
    me in an alpine:latest container.

diff --git a/bin/varnishtest/tests/u00012.vtc b/bin/varnishtest/tests/u00012.vtc
index e9822213a..6c467c887 100644
--- a/bin/varnishtest/tests/u00012.vtc
+++ b/bin/varnishtest/tests/u00012.vtc
@@ -1,5 +1,7 @@
 varnishtest	"trivial run of varnishadm in pass mode"
 
+feature cmd "! grep -q ID=alpine /etc/os-release"
+
 server s1 {
 	rxreq
 	txresp