Comment on Fix “checking build system type… Invalid configuration `x86_64-unknown-linux’: machine `x86_64-unknown’ not recognized” on ./configure by Arthur Helfstein Fragoso.
like @Thibs said the file ‘config.sub’ contains the supported CPUs, if it’s an old version, it wont support newer CPUs.
you can get the latest version of ‘config.sub’ from:
http://git.savannah.gnu.org/gitweb/?p=config.git;a=blob_plain;f=config.sub;hb=HEAD
just copy the latest version of ‘config.sub’ and replace to the one that’s in the folder of what you are trying to run the ./configure
good luck to anyone having the same problem 😉
