maintainer-feedback requested: [Bug 244603] emulators/virtualbox-ose: use contemporary GCC instead of old llvm

[bugzilla-noreply at freebsd.org]

Bugzilla Automation <bugzilla at FreeBSD.org> has asked vbox at FreeBSD.org for
maintainer-feedback:
Bug 244603: emulators/virtualbox-ose: use contemporary GCC instead of old llvm
https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=244603



--- Description ---
The bug in PR 236616 resulted in virtualbox getting pinned to llvm7. This is
less than ideal, and in-fact has been broken by improvements to
machine/atomic.h on x86 that require a more modern compiler.

Switch the build to use GCC9. USE_GCC= any is not sufficient, as GCC8 doesn't
support the feature used by atomic.h. The patches that were previously applied
if COMPILER_TYPE == clang are actually needed by GCC9 as well, so make those
standard patches instead, folding the Config.kmk patches together.

We should put some effort into testing llvm10 and working out why llvm breaks
it, but fixing the build is more important at the moment.

Q/A: 
* portlint (pre-existing issues; none in current patch)
* testport (-CURRENT, amd64)
* run tested by madpilot@