CI: build with GCC 11

[reinerh]

this fixes a new false positive memory leak (#4297), but unfortunately
opens a few new false positives (#4274).
therefore let it ignore memleak checks for now, until the detection
is a bit more stable in GCC.

Fixes: #4274, #4297

ping @smitsohu @rusty-snake @glitsj16 @kmk3

[reinerh]

@smitsohu whitelist.exp test is now failing:

$ firejail --whitelist=~/fjtest-file-lnk --whitelist=~/fjtest-dir-lnk
Reading profile /etc/firejail/default.profile
Reading profile /etc/firejail/disable-common.inc
Reading profile /etc/firejail/disable-passwdmgr.inc
Reading profile /etc/firejail/disable-programs.inc

** Note: you can use --noprofile to disable default.profile **

Parent pid 19111, child pid 19112
Child process initialized in 70.08 ms
user@host:~$ TESTING ERROR 30

the test is doing the following:

# symlinks outside home to a file we don't own
send -- "rm ~/fjtest-file-lnk\r"
after 200
send -- "ln -s /etc/passwd ~/fjtest-file-lnk\r"
after 200
send -- "firejail --whitelist=~/fjtest-file-lnk --whitelist=~/fjtest-dir-lnk\r"
expect {
        timeout {puts "TESTING ERROR 30\n";exit}
        "invalid whitelist path"
}
expect {
        timeout {puts "TESTING ERROR 31\n";exit}
        "cannot sync with peer"
}
sleep 1

it expects that firejail throws an error, when a file is whitelisted that symlinks to outside home.
is this now considered allowed? or a bug in the whitelist?

[smitsohu]

@reinerh These symlink restrictions are gone, so we will need to disable the tests.

[smitsohu]

I'll try to fix the broken tests in a separate pull request. Thanks!