Docs: Add DEPFILE to substitutions list [ci skip]
@@ -679,6 +679,7 @@ argument also accepts the following:
- `@OUTPUT@`: the full path to the output file
- `@INPUT@`: the full path to the input file
+- `@DEPFILE@`: the full path to the depfile
- `@SOURCE_DIR@`: the full path to the root of the source tree
- `@CURRENT_SOURCE_DIR@`: this is the directory where the currently processed meson.build is located in
- `@BUILD_DIR@`: the full path to the root of the build dir where the output will be placed
