Second Eoan Ermine test rebuilds

[Matthias Klose]

The second test rebuild of Eoan Ermine was started on September 06 2019 for
all architectures, all components. The rebuild of the main component is 
finished, the other components (restricted, universe, multiverse) are still 
building.

Unfortunately we see 1300+ build failures, and still counting ...  On the other 
hand the test rebuild includes the recent GCC, glibc packages, and the 
glib2.o/gtk packages synced from experimental.

Results (please also look at the superseded builds) can be found at

https://people.canonical.com/~doko/ftbfs-report/test-rebuild-20190906-eoan.html

The report uses some additional color coding, marking packages different which
always failed to build, or where the build failure is no regression compared to
bionic.  The test rebuild already uses the linux-libc-dev 5.3 package found in 
the ubuntu-toolchain-r/volatile PPA.

Additional build failures for packages in eoan-proposed (not yet in eoan)
can be found at http://qa.ubuntuwire.com/ftbfs/

Please help fixing the build failures.

There is also a test rebuild with link time optimization turned on by default 
(passing -flto=auto in CFLAGS/CXXFLAGS).  Other distributions turned these 
optimzations on by default, or are considering doing that.

https://people.canonical.com/~doko/ftbfs-report/test-rebuild-20190906-lto-eoan.html

Packages to use -flto by default (dpkg) can be found in the
ubuntu-toolchain-r/dpkg-lto PPA. WARNNING: Make sure to install these dpkg 
packages in a throw-away environment.

Matthias