fix: merge '-Wl,' with next value when (#4367)

**What type of PR is this?**

> Bug fix

**What does this PR do? Why is it needed?**

Previously if we pass `-extldflags,-Wl,--thread` into command line, it
will only recognizes `-Wl` and ignores `--thread`.

**Which issues(s) does this PR fix?**
#3921 

Fixes #

If we see `-Wl`, we can merge with next value in the list.

**Other notes for review**

Co-authored-by: zhanning.lu <zhanning.lu@bytedance.com>
1 file changed