testing/check_software: add libanl in system libraries whitelist

libanl is part of glibc since 2001 (see
https://sourceware.org/git/?p=glibc.git;a=blob;f=ChangeLog.old/ChangeLog.12;h=adcf9081d44c06e03c3899612afba7c8c0d9b3fa;hb=HEAD#l5595)

See merge request !291
8 jobs for fix/standalone-all
Status Job ID Name Coverage
  External
passed SlapOS.Eggs.UnitTest-Jerome.Python3

failed SlapOS.Eggs.UnitTest-Master.Python2

00:14:28

failed SlapOS.Eggs.UnitTest-Master.Python3

00:09:36

passed SlapOS.Eggs.UnitTest-Master.Python2

00:31:56

passed SlapOS.Eggs.UnitTest-Master.Python3

00:29:30

passed SlapOS.Eggs.UnitTest-Master.Python3

00:12:33

passed SlapOS.Eggs.UnitTest-Master.Python3

00:06:59

passed SlapOS.Eggs.UnitTest-Master.Python3

00:11:33