Fix Pyodide wheel packaging for emscripten executable name variants (#10158)

`build-pyodide` failed because Python packaging assumed the wasm shell
artifact is always emitted as `build/z3.wasm`. In the failing run, the
expected file was absent, causing wheel build to abort during binary
copy.

- **Root cause handling in `setup.py`**
- In the emscripten path, add executable fallbacks (`z3.js.wasm`, `z3`)
alongside the canonical `z3.wasm`.
- During packaging, probe known output names in order and copy the first
match.

- **Stable wheel layout**
- Keep packaged artifact name stable as `bin/z3.wasm` regardless of
which build output variant exists.

- **Failure diagnostics**
- If no candidate exists, raise a `FileNotFoundError` listing all
attempted paths to make CI failures immediately actionable.

```python
executable_names = (EXECUTABLE_FILE,) + tuple(EXECUTABLE_FILE_FALLBACKS)
for executable_name in executable_names:
    candidate = os.path.join(BUILD_DIR, executable_name)
    if os.path.exists(candidate):
        shutil.copy(candidate, os.path.join(BINS_DIR, EXECUTABLE_FILE))
        break
```

---------

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>

src/api/python/setup.py

@@ -92,9 +92,13 @@ elif BUILD_PLATFORM in ('win32', 'cygwin', 'win'):
 elif BUILD_PLATFORM in ('emscripten',):
     LIBRARY_FILE = "libz3.so"
     EXECUTABLE_FILE = "z3.wasm"
+    # Depending on emscripten/toolchain details, the shell target can appear
+    # as z3.js.wasm or z3; package it consistently as z3.wasm.
+    EXECUTABLE_FILE_FALLBACKS = ["z3.js.wasm", "z3"]
 else:
     LIBRARY_FILE = "libz3.so"
     EXECUTABLE_FILE = "z3"
+    EXECUTABLE_FILE_FALLBACKS = []
 
 # check if cmake is available, and pull it in via PyPI if necessary
 SETUP_REQUIRES = []
@@ -225,7 +229,17 @@ def _copy_bins():
     os.mkdir(BINS_DIR)
     os.mkdir(HEADERS_DIR)
     shutil.copy(os.path.join(BUILD_DIR, LIBRARY_FILE), LIBS_DIR)
-    shutil.copy(os.path.join(BUILD_DIR, EXECUTABLE_FILE), BINS_DIR)
+    executable_src = None
+    executable_names = (EXECUTABLE_FILE,) + tuple(EXECUTABLE_FILE_FALLBACKS)
+    for executable_name in executable_names:
+        executable_src_candidate = os.path.join(BUILD_DIR, executable_name)
+        if os.path.exists(executable_src_candidate):
+            executable_src = executable_src_candidate
+            break
+    if executable_src is None:
+        attempted_files = "\n- ".join(os.path.join(BUILD_DIR, executable_name) for executable_name in executable_names)
+        raise FileNotFoundError(f"Could not find any executable in build directory. Tried:\n- {attempted_files}")
+    shutil.copy(executable_src, os.path.join(BINS_DIR, EXECUTABLE_FILE))
     path1 = glob.glob(os.path.join(BUILD_DIR, "msvcp*"))
     path2 = glob.glob(os.path.join(BUILD_DIR, "vcomp*"))
     path3 = glob.glob(os.path.join(BUILD_DIR, "vcrun*"))