In 4.18 and 4.19, it is no longer possible to build the ShaderCacheTool.
Yes. The ShaderCacheTool builds successfully in 4.17.2. It looks like the missing MergeShaderCacheFiles property was removed in CL 3574705.
The build fails with the following error messages:
The build completes successfully.
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-52566 in the post.