Support for outputting a list of user/system dependencies (dependency file generation)

[squeek502]

Note: this is related / possibly a duplicate of #239

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Personally I only need the equivalent of -MD that can be retrieved when using Aro as a library (i.e. an ArrayList in/given to Compilation or Preprocessor that gets populated during preprocessing).

Relevant clang CLI docs: https://clang.llvm.org/docs/ClangCommandLineReference.html#dependency-file-generation

Dependency file generation

Flags controlling generation of a dependency file for make-like build systems.

-M, --dependencies

Like -MD, but also implies -E and writes to stdout by default

-MD, --write-dependencies

Write a depfile containing user and system headers

-MF<file>

Write depfile output from -MMD, -MD, -MM, or -M to <file>

-MG, --print-missing-file-dependencies

Add missing headers to depfile

-MJ<arg>

Write a compilation database entry per input

-MM, --user-dependencies

Like -MMD, but also implies -E and writes to stdout by default

-MMD, --write-user-dependencies

Write a depfile containing user headers

-MP

Create phony target for each dependency (other than main file)

-MQ<arg>

Specify name of main file output to quote in depfile

-MT<arg>

Specify name of main file output in depfile

-MV

Use NMake/Jom format for the depfile

[squeek502]

Closing this as I think Compilation.sources will work for my use case. #239 is the better issue for this as a general concept.