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 https://github.com/redis/redis/issues/6275 and https://github.com/yahoo/redislite/issues/150

This change to the Makefile in redis.submodule (fix from https://github.com/redis/redis/commit/f5d48537f1aa76e5ce4f14953517bd25c9ad4673) 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?