cosbench-ecs is not recognized as a subproject in Eclipse

[thatsdone]

DESCRIPTION

cosbench-ecs does not appear as a part of COSBench driver projects inside Eclipse IDE environment.

REPRODUCE PROCEDURE

Just try to build COSBench following BUILD.md, you would notice that cosbench-ecs does not apppear.

ANALYSYS and SUGGESTED RESOLUTION

Actually, this issue was already poitend out by @Nathaniel7687 in 2018 and
can be resolved by chunks of his PR (#373).

Please feel that this is a kind of effort to break down a complex phoenomea into
organized issues.