Add C/C++ header dependency finder.
build: Improve generated command script.
command: Make it flat to simplify further parsing operations.
command: Add outputs getter.
compiler: Add specific Source and IncludeDirectory node types.
generator: Fix closing function name.
generators.makefile: Update to the new generator interface.
generators.tup: Update to the new generator interface.
lang.c.gcc: Remove useless build flag "no-canonical-prefixes"
lang.c.library: Clean up directory paths.
node: Allow absolute shell formatting.
path: Expand ~ in paths.
Use no-common flag by default.