* remove everything that causes conflicts when installing gcc6 and
  gcc6-armhf side by side
* fix up the existing "if cross compiling" code path to use the
  /usr/gcc6 prefix
* link binutils binaries to the locations they are expected to be
  by gcc (this took me hours to figure out....) as well as by the
  linux build system with CROSS_COMPILE
* link all gcc binaries to /usr/bin/gcc6-*

Based on the last version from Alpine, but installed to /usr/gcc6 and
with pretty much everything disabled except for the C compiler.

We can probably throw out a lot of patches, and make the APKBUILD much
smaller. But let's focus on making it possible to compile old kernels
again first. There's still a lot to do for that, see #103.

Skipping CI, because it would probably not finish building all of them.
Major breakage incoming. Details discussed here:
<https://gitlab.com/postmarketOS/pmaports/issues/103>

I've missed the patch files in the previous commit, my bad.

This reverts commit 71ffb785.

This test case only makes sense in the pmbootstrap repository, and
we have it there already. In pmaports, we don't need to check if the
"aportgen" code is working - and to check the versions of the aports
we already have the test_upstream_compatibility case.

Got the info from:
<https://developer.puri.sm/Environments/PlasmaMobile.html>

* Added linux-postmarketos-allwinner kernel
* Added copy of alpines u-boot package with pine-a64lts support
* Changed postmarketos-mkinitfs to add the plain .dtb file to the boot partition

If hildon-desktop doesn't build, then it doesn't make sense to build
the rest right now - and it's likely that this won't build either.

Build is failing.

Weston does not build for x86, because it depends on libunwind. And
libunwind is not available in Alpine for x86. I've also tried to
simply enable x86 in libunwind, but it does not build out of the box.

In order to start building again for x86 at all, let's disable weston
and all packages that depend on it on for now.

ecm_find_qmlmodule checks if QML modules are installed, and if not it
warns during build time. This is purely for packager knowledge. Not
finding those packages here doesn't affect the runtime of the
kwin_wayland at all.

We are disabling this due to bug in the qmlplugindump which causes it to
not return and get stuck, See issue #28.

Revert this when QTBUG-70460 is solved upstream.

so:libprotobuf.so.15 does not exist anymore in Alpine edge

When cross compiling, the kernel scripts would be in the native arch
again. That was already fixed in !1234, however the mime type of the
binaries has changed, so we couldn't detect them properly anymore
(#1659).

This commit fixes it again, and also adds a checks so this won't
silently fail in the future.

[skip ci] because this would not run through anyway (building these
packages takes too long). Fixes #1659.

Update happened upstream in Alpine edge:
https://github.com/alpinelinux/aports/pull/4983

Copy all test cases from the pmbootstrap repository, that are actually
testing the aports. They were all adjusted to work nicely in this
repository, together with a brand new set of gitlab-ci configs.

This also includes the changes from this merge request, that had a
better detection of changed packages:
<https://gitlab.com/postmarketOS/pmbootstrap/merge_requests/1621>