Do not suppress EOFError/KeyboardInterrupt when standalone is disabled

Raise Abort() exception in a chain with the original exception.

src/click/core.py

@@ -1063,9 +1063,9 @@ def main(
                     # even always obvious that `rv` indicates success/failure
                     # by its truthiness/falsiness
                     ctx.exit()
-            except (EOFError, KeyboardInterrupt):
+            except (EOFError, KeyboardInterrupt) as e:
                 echo(file=sys.stderr)
-                raise Abort() from None
+                raise Abort() from e
             except ClickException as e:
                 if not standalone_mode:
                     raise

tests/test_commands.py

@@ -411,3 +411,15 @@ def command2(e):
 
     runner.invoke(group, ["command1"])
     assert opt_prefixes == {"-", "--", "~", "+"}
+
+
+@pytest.mark.parametrize("exc", (EOFError, KeyboardInterrupt))
+def test_abort_exceptions_with_disabled_standalone_mode(runner, exc):
+    @click.command()
+    def cli():
+        raise exc("catch me!")
+
+    rv = runner.invoke(cli, standalone_mode=False)
+    assert rv.exit_code == 1
+    assert isinstance(rv.exception.__cause__, exc)
+    assert rv.exception.__cause__.args == ("catch me!",)