There are a few changes in glibc-2.10 that might make your software fail to build with it, please refer to my blog post  if you're not sure what the problem is.
And no I don't usually provide emerge --info with these bugs because they are caused by glibc-2.10!
Created attachment 193464 [details]
Created attachment 194821 [details, diff]
patches 4.2.15 strongswan ebuild / use sed to rename function / avoid function name collision between pkg's getline() and glibc's getline()
either put strongswan-9999 ebuild into portage or use this patch to let 4.2.15 of strongswan compile on systems w/ glibc >= 2.10
Thanks, patch applied for 4.2.15 and 4.2.16. Also committed 4.3.2 as per security bug 275096.