get.py on aarch64 will get toolchain for wrong architecture.

[lobradov]

Basic Info

When trying to get binary toolchain, arm64v8 (aarch64) platform is wrongly identified as x86_64.
Problem is in the get.py script, identify_platform().

Description

$ uname -a
Linux orangepiprime-01 4.14.8-sunxi64 #68 SMP Thu Dec 21 12:52:19 CET 2017 aarch64 aarch64 aarch64 GNU/Linux

$ ./get.py 
Platform: x86_64-pc-linux-gnu
Downloading esptool-0.4.12-linux64.tar.gz
Done
Extracting dist/esptool-0.4.12-linux64.tar.gz
Renaming esptool-0.4.12-linux64 to esptool
Downloading linux64-xtensa-lx106-elf-gb404fb9.tar.gz
Done
Extracting dist/linux64-xtensa-lx106-elf-gb404fb9.tar.gz
Downloading mkspiffs-0.2.0-no_magic_length-linux64.tar.gz
Done
Extracting dist/mkspiffs-0.2.0-no_magic_length-linux64.tar.gz
Renaming mkspiffs-0.2.0-no_magic_length-linux64 to mkspiffs