buildman: Enable buildman on aarch64 hosts

At kernel.org aarch64 toolchains are published in folder
arm64. Fix the URL for that case, so that we can fetch
toolchains on aarch64 machines.

Signed-off-by: Matthias Brugger <mbrugger@suse.com>
Reviewed-by: Simon Glass <sjg@chromium.org>

tools/buildman/toolchain.py

@@ -487,6 +487,8 @@ class Toolchains:
                 URL containing this toolchain, if avaialble, else None
         """
         arch = command.OutputOneLine('uname', '-m')
+        if arch == 'aarch64':
+            arch = 'arm64'
         base = 'https://www.kernel.org/pub/tools/crosstool/files/bin'
         versions = ['7.3.0', '6.4.0', '4.9.4']
         links = []