Build Guide: Add steps for Fedora Linux (#1333)
Build Guide: Add steps for Fedora Linux (#1333)

* Build Guide: Add steps for Fedora Linux

- Add separate steps for fedora
- Change title for apt based linux steps to 'Ubuntu/Debian Linux'

Test: Steps were tested on a dragonboard410c running aarch64
       variants of debian buster and fedora 28

Signed-off-by: Sahaj Sarup <f57f81cea0b0643756ec4bc65188a4e17303238f@linaro.org>

* Update README.md

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