app.update.url does not exist anymore:
https://bugzilla.mozilla.org/show_bug.cgi?id=1568994

At the same time we remove the MBSDIFF environment variable as it is not
needed for full .mar file generation.

To get nightly builds going we use Mozilla's cross-compiled compiler-rt
for now.

Clean-up and getting us closer to the way Mozilla is deploying the
cross-compilation setup.

We use the somewhat surprising breakage due to
https://bugzilla.mozilla.org/show_bug.cgi?id=1619504 to clean up our
fxc2 build and usage.

Previously, we built both the 64bit and 32bit version of fxc2 and were
running them in a 64bit and 32bit Wine environment, respectively.
However, that's not needed because a) Wine is capable of running both
64bit and 32bit binaries and b) fxc2 is only used at build time to
generate shader files. As we are building both Windows flavors in a
64bit container we should easily be able to live with just a 64bit
variant.

We need, nevertheless, take care that we still bundle the correct
d3dcompiler_47.dll library for the respective architecture.

The sort patch is not needed anymore as the reproducibility issue
got fixed with commit 1405ac457b8b583215cf92d73fbe4479f7c86029 in
libcxx.

--enable-strip is gone for Windows, see:
https://hg.mozilla.org/mozilla-central/rev/943fe6210744.

We rebase the libunwind related patch for 32bit Windows for
compatibility with Rust 1.41.1, too.

We "re-use" the same vendored tarball filename for now as lucetc has not
been used previously anyway.

DBM is not built by default anymore since
https://bugzilla.mozilla.org/show_bug.cgi?id=1594933 landed.

The --enable-signmar option is gone with
https://bugzilla.mozilla.org/show_bug.cgi?id=1562952. The signmar tool
is always built now.

We remove our fenix-node project, too, as there is no difference
between it and the node project anymore. It seems both ESR and non-ESR
are using the same version for the time being.

We can't build the crt in the compiler-rt project on Linux anymore and
work around it by disabling that part. This is likely yet another sign
of Debian Wheezy showing its age.

Apart from that, we should use our own binutils and not whatever Wheezy
is providing.

We'll update abicheck.cc in a follow-up commit (bug 34359).

Additionally, we clean up the project to remove unused parts.

Based on a patch by sisbell, thanks!

We add a new project to not interfere with Fennec toolchain
requirements for now until we stop building Fennec-based Tor Browser
for Android.

Based on a patch by sisbell, thanks!

We add a new project to not interfere with Fennec toolchain
requirements for now until we stop building Fennec-based Tor Browser
for Android.

We remove --libdir as well for the Fenix toolchain as it does nothing
(and would be wrongly used anyway if pointing to ANDROID_NDK_HOME).

Many thanks to boklm for the invaluable help with this patch.

We include a new project, geckoview. While this increases the
boilerplate a bit it should make it easier to move mobile to the regular
release series while desktop stays on ESR, and it is conceptually
clearer as well (no, we don't build firefox on mobile but a library to
be consumed by other projects).