LAKITU: add QEMU 5.2.0 from the Gentoo upstream

Performance of QEMU up to 5.2.0 is severely affected by the compiler.
The clang build is 100 times slower than GCC build when measured by
this microbenchmark: dd if=/dev/zero bs=1M count=256 | md5sum
This performance issue causes systemd services time out during
boot up and renders booted COS image unusable.

There is no clean way to force-rebuild QEMU when setting up chroot
so instead bring 5.2.0 from the Gentoo upstream to chromiumos-overlay
as the most future-proof workaround. Once portage-stable version
catches up and overtakes 5.2.0, it'll be used instead of this ebuild.

ncurses flag has to be disabled because 5.2.0 requires ncurses 6
which has not been ported from the upstream yet.

TEST=run VMtest using new version of QEMU

Change-Id: I0f6717c6d9f6de08f5584375063c3d6428e93e05
Reviewed-by: Roy Yang <>
Tested-by: Cusky Presubmit Bot <>
13 files changed