Taichi built from source takes too long time

[BillXu2000]

Describe the bug
When building taichi from source, it seems that the compilation phase is blocked at

Linking CXX static library external/SPIRV-Cross/libspirv-cross-c.ac

This linking takes more than 5 minutes (before I end up this command).

To Reproduce
I built Taichi on Ubuntu 20.04.

commit 4512ccc works on my machine, and the next commit 7262bb0 will trigger this problem.

PR #4716 between this two commits might be the cause of this problem.

[qiao-bo]

The linking phase works fine on my PC. Similar time between the two commits. Can you share your build flags as well?

[PGZXB]

@BillXu2000 Did you use gcc to build? (I think I know why If you used gcc, I am trying to fix a similar problem, pr: #4823