Add support for dynamic dependencies as byproduct of script body

Specifically, the `depdb dyndep` builtin now has the --byproduct option (which
must come first). In this mode only the --file input is supported. For example:

obje{hello.o}: cxx{hello}
{{
  o = $path($>)
  t = $(o).t

  depdb dyndep --byproduct --what=header --default-type=h --file $t

  diag c++ ($<[0])

  $cxx.path $cxx.poptions $cc.poptions $cc.coptions $cxx.coptions $cxx.mode -o $o -MD -MF $t -c $path($<[0])
}}

Naturally, this mode does not support dynamic auto-generated prerequisites.
If present, such prerequisites must be specified statically in the buildfile.

Note also that the --default-prereq-type option has been rename to
--default-type.

1 files changed, 26 insertions, 9 deletions

diff --git a/libbuild2/build/script/builtin-options.hxx b/libbuild2/build/script/builtin-options.hxx
index 85d67b9..15119f4 100644
--- a/libbuild2/build/script/builtin-options.hxx
+++ b/libbuild2/build/script/builtin-options.hxx
@@ -297,10 +297,10 @@ namespace build2
   {
     namespace script
     {
-      class depdb_dep_options
+      class depdb_dyndep_options
       {
         public:
-        depdb_dep_options ();
+        depdb_dyndep_options ();
 
         // Return true if anything has been parsed.
         //
@@ -404,19 +404,34 @@ namespace build2
         include_path_specified (bool);
 
         const string&
-        default_prereq_type () const;
+        default_type () const;
 
         string&
-        default_prereq_type ();
+        default_type ();
 
         void
-        default_prereq_type (const string&);
+        default_type (const string&);
 
         bool
-        default_prereq_type_specified () const;
+        default_type_specified () const;
 
         void
-        default_prereq_type_specified (bool);
+        default_type_specified (bool);
+
+        const dir_path&
+        cwd () const;
+
+        dir_path&
+        cwd ();
+
+        void
+        cwd (const dir_path&);
+
+        bool
+        cwd_specified () const;
+
+        void
+        cwd_specified (bool);
 
         // Implementation details.
         //
@@ -439,8 +454,10 @@ namespace build2
         bool what_specified_;
         dir_paths include_path_;
         bool include_path_specified_;
-        string default_prereq_type_;
-        bool default_prereq_type_specified_;
+        string default_type_;
+        bool default_type_specified_;
+        dir_path cwd_;
+        bool cwd_specified_;
       };
     }
   }