[Bug lto/54206] build in source dir breaks lto plugin detection

[andi-gcc at firstfloor dot org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54206

--- Comment #2 from Andi Kleen <andi-gcc at firstfloor dot org> 2012-08-09 12:39:14 UTC ---
I didn't do it, but I had to debug a user's gcc config who did it.

WONTFIX would be wrong, if you really don't support it error out in configure
please instead of silent breakage (glibc does that).
But fixing it would be better I think.