many:1 rules

So I'm thinking on a way to express a custom build rule that represents a many:1 input:output relationship.
Custom rules currently map sourcefile->outputfile as 1:1, by executing the commandlines on each input file.
Consider the linker pattern though by contrast, which accepts all obj files and outputs a single exe... I have encountered numerous cases where I want a custom rule to accept all input files of the input file type at once, and then emit a single output by a single invocation of the build tool.
Custom rules should be able to express this.

I can easily think of lots of moderately hideous tweaks to rule where I could contort premake to understand this configuration, but I put this out there to others to get fresh perspectives...

If you were approaching this problem, how would you naturally plan to solve it? I don't want to pollute your thoughts with my own ideas (which I don't really like).

The issue does not name files, tests, or entry points. Start by locating the existing custom-rule mapping and linker handling, then determine how a rule could accept all inputs of a type and emit one output in a single invocation; done means the behavior and configuration are defined clearly enough to implement and test.