Add support for dynamic dependencies in ad hoc Buildscript recipes

Specifically, add the new `depdb dyndep` builtin that can be used to extract
dynamic dependencies from a program run or a file. For example:

obje{hello.o}: cxx{hello}
{{
  s = $path($<[0])

  depdb dyndep $cxx.poptions $cc.poptions --what=header --default-prereq-type=h -- $cxx.path $cxx.poptions $cc.poptions $cxx.mode -M -MG $s

  diag c++ ($<[0])

  o = $path($>)
  $cxx.path $cxx.poptions $cc.poptions $cc.coptions $cxx.coptions $cxx.mode -o $o -c $s
}}

Currently only the `make` dependency format is supported.

1 files changed, 32 insertions, 0 deletions

diff --git a/libbuild2/build/script/builtin.cli b/libbuild2/build/script/builtin.cli
new file mode 100644
index 0000000..3ed3659
--- /dev/null
+++ b/libbuild2/build/script/builtin.cli
@@ -0,0 +1,32 @@
+// file      : libbuild2/build/script/builtin.cli
+// license   : MIT; see accompanying LICENSE file
+
+include <libbuild2/types.hxx>;
+
+// Note that options in this file are undocumented because we generate neither
+// the usage printing code nor man pages. Instead, they are documented in the
+// manual.
+//
+namespace build2
+{
+  namespace build
+  {
+    namespace script
+    {
+      // Pseudo-builtin options.
+      //
+      class depdb_dep_options
+      {
+        // Note that --byproduct, if any, must be the first option and is
+        // handled ad hoc, kind of as a sub-command.
+        //
+        path --file;                   // Read from file rather than stdin.
+        string --format;               // Dependency format: make (default).
+        string --what;                 // Dependency kind, e.g., "header".
+        dir_paths --include-path|-I;   // Search paths for generated files.
+        string --default-prereq-type;  // Default prerequisite type to use
+                                       // if none could be derived from ext.
+      };
+    }
+  }
+}