reloc/build_reloc.sh: find ninja-build after executed install-dependencies.sh
reloc/build_reloc.sh: find ninja-build after executed install-dependencies.sh

The build environment may not installed ninja-build before running
install-dependencies.sh, so do it after running the script.

Signed-off-by: Takuya ASADA <4ebfb6f510af412d6e89fefa3ab96d9c8b5e3fff@scylladb.com>
Message-Id: <20181031110737.17755-1-4ebfb6f510af412d6e89fefa3ab96d9c8b5e3fff@scylladb.com>

scylladb/scylla,avikivity/scylla,scylladb/scylla,avikivity/scylla,avikivity/scylla,scylladb/scylla,scylladb/scylla