build: Compile `fmt` as a static library
build: Compile `fmt` as a static library

This restores the old behavior of the build, and makes integration with
Scylla easier.

It's still possible to provide `fmt` from anywhere on the system,
including as a shared library, but not with `configure.py`.

Signed-off-by: Jesse Haber-Kucharsky <526eadea4792054b99d5fa5dd6be9acdd76c5418@scylladb.com>
Message-Id: <00a19e69ddd23c2b9b3e5cdeeb8af6650fc7a9ef.1547531306.git.526eadea4792054b99d5fa5dd6be9acdd76c5418@scylladb.com>

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