buildman/toolchain.py: handle inconsistent tarball names

buildman/toolchain.py: handle inconsistent tarball names

Unfortunately, for some releases the kernel.org toolchain tarball names adhere
to the following pattern:

	<hostarch>-gcc-<ver>-nolib-<targetarch>-<type>.tar.xz

e.g.:
	x86_64-gcc-8.1.0-nolibc-aarch64-linux.tar.xz

while others use the following pattern:

	<hostarch>-gcc-<ver>-nolib_<targetarch>-<type>.tar.xz

e.g.:

	x86_64-gcc-7.3.0-nolibc_aarch64-linux.tar.xz

Notice that the first pattern has dashes throughout, while the second has
dashes throughout except just before the target architecture which has an
underscore.

The "dash throughout" versions from kernel.org are:

	8.1.0, 6.4.0, 5.5.0, 4.9.4, 4.8.5, 4.6.1

while the "dash and underscore" versions from kernel.org are:

	7.3.0, 4.9.0, 4.8.0, 4.7.3, 4.6.3, 4.6.2, 4.5.1, 4.2.4

This tweak allows the code to handle both versions. Note that this tweak also
causes the architecture parsing to get confused and find the following two
bogus architectures, "2.0" and "64", which are explicitly checked for, and
removed.

Signed-off-by: Trevor Woerner <trevor@toganlabs.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
Change single quotes to double quotes:
Signed-off-by: Simon Glass <sjg@chromium.org>