jw.pkg.App: Support --topdir-format

Add support for --topdir-format. The option supports several different values, affecting the console output of App wherever it knows that the output contains a reference to the projects' toplevel directory.
  - "unaltered" will have it print the toplevel directory in the same
    format as passed to the commandline
  - "absolute" will try to resolve it to an absolute path before
    printing
- make:XXX will return the make-varible $(XXX) instead
To implement this, the proj_dir() member function is turned into the private member function __proj_dir(), and a new member function find_dir() is supplied, with two additional parameters: search_subdirs and search_absdirs, which will try to find an existing directory relative to the toplevel directory of the given module, or in the search_absdirs list, respectively.
Command modules in cmds.projects have been updated to use the new function.
Signed-off-by: Jan Lindemann <jan@janware.com>

src/python/jw/pkg/cmds/projects/CmdCflags.py

@@ -16,13 +16,10 @@ class CmdCflags(Cmd): # export
     def _run(self, args: Namespace) -> None:
         deps = self.app.get_modules_from_project_txt(args.module, ['pkg.requires.jw'], 'build',
                 scope = 2, add_self=True, names_only=True)
-        r = ''
+        out = []
         for m in reversed(deps):
-            try:
-                pd = self.app.proj_dir(m)
-                if pd is None:
-                    continue
-                r = r + ' -I' + pd + '/include'
-            except Exception as e:
-                self.app.warn(f'No include path for module "{m}", ignoring: {e}')
-        print(r[1:])
+            path = self.app.find_dir(m, ['/include'])
+            if path is not None:
+                out.append('-I' + path)
+        if out:
+            print(' '.join(out))