incrementally add sources + headers to lib using blt

[cyrush]

request from visit team:

we would like to be able to call blt_add_library, and then add sources + headers incrementally after the lib is added.

We have source files for libs that span directories, curating a list with all sources before we call blt_add_library requires extra bookkeeping.

We do want all of our sources to have the blt processing logic that blt_add_library provides.

[biagas]

Any thoughts on when this could be implemented?

[white238]

I unfortunately don't. I hope to have some BLT specific time at the beginning of the fiscal year.