Use append action instead of nargs for cmake defs in x.py

[PragmaTwice]

Currently, we use nargs=* for parsing -D arguments, e.g. -D X=1 Y=2 -> ["X=1", "Y=2"], -D X=1 -D Y=2 -> ["Y=2"].

We need to change it to action=append to align the behavior with CMake, e.g. -D X=1 -D Y=2 -> ["X=1", "Y=2"].

It solved #1254 and fix all wrong argument parsing in GitHub Actions.

[tisonkun]

LGTM. May I ask the disk_stats related changes? We'd better avoid mixing changes, or at least describe what it is.

[PragmaTwice]

LGTM. May I ask the disk_stats related changes? We'd better avoid mixing changes, or at least describe what it is.

Previously, all ASan and TSan checks in CI have never been applied (only the last -D was kept, all other cmake defs were ignored), so I try to solve all ASan and TSan reports to make the CI pass.

[tisonkun]

Thanks for your explanation! That's reasonable.

[PragmaTwice]

Thanks all. Merging...