tizen: Guess system arch
tizen: Guess system arch

There is no reason to hardcode this,
when It can be guessed at build time.

Even %_arch is not reliable, for instance Fedora-24 on ARTIK7
defines %_arch as "arm".

Bug: https://jira.iotivity.org/browse/IOT-524
Change-Id: I545ba2b5128291951e47f7e98a2932af994187f6
Origin: https://github.com/TizenTeam/iotivity/tree/sandbox/pcoval/on/master/fedora
Forwarded: https://gerrit.iotivity.org/gerrit/#/c/23497/
Signed-off-by: Philippe Coval <ff46fec9739d31cce915aabcc3a7a2c00eee4d6c@osg.samsung.com>

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