By default, wget prints dots every 1k bytes. This can render a
lot of output for large files. We switch to the "mega" style, which
makes each dot represent 64k, thus reducing output by up to 64x.
We also force the use of dot display. By default, it uses "bar"
which attempts to use terminal formatting if possible. Since most
of this code executes in CI and terminal control characters can
interfere with logged output, we force the use of "dot." (Although
wget appears to automatically switch to dot in TC today. But
consistency is good.)
MozReview-Commit-ID: IpTWJdcauTV
The "contract" for toolchains is that extracting foo.tar.xz creates a
directory named foo/. That is however not true for mingw32.tar.xz, which
extracts into gcc/, possibly overwriting files from the gcc.tar.xz
archive (which is also used for mingw builds, for the host part).
This is also not true for nsis.tar.xz, but it reportedly has problems
when it's not in the same directory as mingw32.
But mingw32 doesn't actually need to be mixed with gcc, so it's better
to separate them as they are supposed to be.
