[DRE-maint] Bug#995716: ruby3.0 accesses the internet during the build

[Adrian Bunk]

Source: ruby3.0
Version: 3.0.2-2
Severity: serious
Tags: ftbfs

https://buildd.debian.org/status/fetch.php?pkg=ruby3.0&arch=amd64&ver=3.0.2-2&stamp=1633362344&raw=0

...
  1) Failure:
TestSocket_TCPSocket#test_initialize_connect_timeout [/<<PKGBUILDDIR>>/test/socket/test_tcp.rb:73]:
[Errno::ETIMEDOUT] exception expected, not #<Errno::ENETUNREACH: Network is unreachable - connect(2) for "192.0.2.1" port 80>.

Finished tests in 791.435806s, 26.6073 tests/s, 3379.8319 assertions/s.
21058 tests, 2674920 assertions, 1 failures, 0 errors, 103 skips

ruby -v: ruby 3.0.2p107 (2021-07-07 revision 0db68f0233) [x86_64-linux-gnu]
make[2]: *** [uncommon.mk:800: yes-test-all] Error 1



The FTBFS is on an IPV6-only buildd, but this is forbidden
internet accesss during the build in any case.