I need to build some of the boost libraries for ARM. I followed the instructions here: https://www.boost.org/doc/libs/1_58_0/more/getting_started/unix-variants.html and I get the following error when running "b2 --toolset=gcc":

aarch64-linux-gnu-g++: error: unrecognized command line option ‘-m64’

If it means anything, before the error I get:

Performing configuration checks

    - 32-bit                   : no  (cached)
    - 64-bit                   : yes (cached)
    - arm                      : no  (cached) // is this right?

Building the Boost C++ Libraries.
    - x86                      : no  (cached)
    - arm                      : no  (cached) // ?

My project-config.jam has:
using gcc : arm : aarch64-linux-gnu-g++ ; // also tried arm64, aarch64-linux-gnu-gcc

Any help appreciated.

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