Add new GitLab runner for gitlab.bsc.es

It uses docker based on alpine and the host nix store, so we can perform
builds but isolate them from the system.

secrets/gitlab-bsc-docker-token.age

@@ -0,0 +1,11 @@
+age-encryption.org/v1
+-> ssh-ed25519 HY2yRg WSdjyQPzBJ4JbzQpGeq1AAYpWKoXmLI1ZtmNmM5QOzs
+qGDlDT31DQF1DdHen0+5+52DdsQlabJdA2pOB5O1I6g
+-> ssh-ed25519 CAWG4Q wioWMDxQjN+d4JdIbCwZg0DLQu1OH2mV6gukRprjuAs
+670fE61hidOEh20hHiQAhP0+CjDF0WMBNzgwkGT8Yqg
+-> ssh-ed25519 MSF3dg DN19uvAEtqq4708P6HpuX9i/o/qAvHX6dj69dCF2H1o
+4Lu9GnjiFLMeXJ2C7aVPJsCHCQVlhylNWJi896Av92s
+--- 7cKBwOYNOUZ2h3/kAY09aSMASZSxX7hZIT4kvlIiT6w
+<EFBFBD>6<EFBFBD><02><><EFBFBD><06>fQF5=<3D>bX+<2B>v e`<60>7/<2F><05>A~P<><50>Ѧ7<15><>
+<EFBFBD><EFBFBD>A<EFBFBD>)<29>h<05><>=oZ<6F>$<24>^<5E>V0<56>/܅<>r
+k<EFBFBD>u<EFBFBD>bĶ:R<><52>>^g<><67><06>ik_*%<0B>a7<61>KG<4B><47><EFBFBD><EFBFBD><EFBFBD><EFBFBD>&<26>PI<50><49>n