Don't pass --allow-shlib-undefined to lld if it's not supported

Fixes builds with llvm-mingw

mesonbuild/linkers.py

@@ -659,7 +659,18 @@ class LLVMDynamicLinker(GnuLikeDynamicLinkerMixin, PosixDynamicLinkerMixin, Dyna
     This is only the posix-like linker.
     """
 
-    pass
+    def __init__(self, *args, **kwargs):
+        super().__init__(*args, **kwargs)
+
+        # Some targets don't seem to support this argument (windows, wasm, ...)
+        _, _, e = mesonlib.Popen_safe(self.exelist + self._apply_prefix('--allow-shlib-undefined'))
+        self.has_allow_shlib_undefined = not ('unknown argument: --allow-shlib-undefined' in e)
+
+    def get_allow_undefined_args(self) -> typing.List[str]:
+        if self.has_allow_shlib_undefined:
+            return self._apply_prefix('--allow-shlib-undefined')
+        return []
+
 
 
 class CcrxDynamicLinker(DynamicLinker):