merge revision(s) 86022167461dc90b70164e2bb23316959bbfd6ba,47a1872cd8b901b8aab6dedce7fa3807c97d290d: [Backport #16681]
Switch to download libffi source package to github releases from sourceware.org Use osuosl instead of GitHub releases Because the package provided by GitHub releases is different from sourceware.
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_2_6@67842 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
merge revision(s) 86022167461dc90b70164e2bb23316959bbfd6ba,47a1872cd8b901b8aab6dedce7fa3807c97d290d: [Backport #16681]
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_2_6@67842 b2dd03c8-39d4-4d8f-98ff-823fe69b080e