[Reproducible-builds] Bug#777753: gcc: LTO produces unreproducible debug information

[conchur at web.de]

The patches are now upstream [1, 2].

> The last test [2] showed that these really seemed to be the culprit of
> the problem. In the meantime, Richard Biener proposed patches which can
> solve this problem. I've compiled my own version of gcc-4.9 using the
> attached patch and can confirm that the LTO builds are now working
> perfectly fine and no changes to the affected packages are necessary
> anymore.

I have to correct my last statement. It is still necessary to add
-flto-partition=none when using -flto in a package. My earlier statement
came from the wrong understanding of buildid as explained in the gcc bug [3].

I've used the updated patches in my tests (see attachment)

[1] https://gcc.gnu.org/viewcvs/gcc?view=revision&revision=220678
[2] https://gcc.gnu.org/viewcvs/gcc?view=revision&revision=220613
[3] https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65015#c9
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