Explicitly link with libatomic if on ARM (Fixes #150)

[alejzeis]

Installation on a Raspberry Pi 4 fails due to Redis failing to link automatically with libatomic. Further discussion in redis/redis#6275 and #150

This change to the Makefile in redis.submodule (fix from redis/redis@f5d4853) explicitly links to libatomic if the architecture is ARM. With this change, compiling and linking succeeds and the installation of redislite succeeds

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[Atoxis]

Hi @alejzeis,

Any update about redislite on ARM ?
This isssue is open since almost one year.

[dwighthubbard]

The contents of the redis.submodule directory get overwritten when the bundled redis is updated. Does this issue exist with redis 6.2.6?