CmdBuild.run(): Build projects that only have a Makefile

A workspace project directory that has a Makefile but no package proofs -
no project.conf, no VERSION - is buildable with a plain make, yet the build
fails on it: calculate_order() walks the requested modules, and the walk in
App.__get_project_refs() raises an unmet dependency, because the
installation state of such a project is unprovable.  The walk has to stay
strict: its proofs are package proofs, and loosening App.is_installed()
would weaken the unmet dependency detection for every get_project_refs()
caller.

This commit therefore keeps the tolerance in the build: before calculating
the order, run() partitions the requested modules. A module that is not
installed in any flavour but resolves to a workspace directory with a
Makefile is appended to the build order as a dependency-less leaf and built
with a plain make; modules without any directory at all still raise the
unmet dependency error. A jw dependency declared in a project.conf on such
a project still raises, which is correct: it is a declared dependency on a
package that does not exist.

Assisted-by: unsloth/Qwen3.8-27B-GGUF:Q4_K_M with pi.dev v0.85.1
Signed-off-by: Jan Lindemann <jan@janware.com>

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

@@ -283,7 +283,29 @@ class CmdBuild(Cmd):  # export
                 log(NOTICE, 'Using prerequisite flavours ' + ' '.join(dep_flavours))
                 log(NOTICE, 'Calculating order for modules ... ')
 
-            calculate_order(order, modules, dep_flavours)
+            def is_makefile_only(m: str) -> bool:
+                # Not installed as a package (no project.conf, no VERSION),
+                # but a project directory with a Makefile in the workspace:
+                # buildable with a plain make, no jw dependencies to read.
+                if self.app.is_installed(m, devel = True) \
+                        or self.app.is_installed(m, devel = False):
+                    return False
+                try:
+                    wd = proj_dir(m)
+                except Exception:
+                    return False
+                return wd is not None and os.path.exists(f'{wd}/Makefile')
+
+            makefile_only = {m for m in modules if is_makefile_only(m)}
+            for m in sorted(makefile_only):
+                log(
+                    NOTICE,
+                    f'Project {m} is not installed, building it as a plain '
+                    f'Makefile project'
+                )
+            calculate_order(order, modules - makefile_only, dep_flavours)
+            for m in sorted(makefile_only):
+                order.append(m)
             if args.ignore_deps:
                 order = [m for m in order if m in args.modules]
             order = [m for m in order if m not in exclude]