I have used to ldc2(1.20.1) on x86-64 laptop with `ldc2 -c
-betterC -mtriple=riscv64 betterC.d -v ` but comiple is failed.
output:
```
binary /usr/bin/ldc2
version 1.20.1 (DMD v2.090.1, LLVM 10.0.0)
config /etc/ldc2.conf (riscv64)
'generic' is not a recognized processor for this target (ignoring
processor)
'generic' is not a recognized processor for this target (ignoring
processor)
...
import core.stdc.time
(/usr/lib/ldc/x86_64-linux-gnu/include/d/core/stdc/time.d)
semantic betterC
/usr/lib/ldc/x86_64-linux-gnu/include/d/core/stdc/time.d(151):
Error: undefined identifier time_t, did you mean function time?
/usr/lib/ldc/x86_64-linux-gnu/include/d/core/stdc/time.d(151):
Error: undefined identifier time_t, did you mean function time?
/usr/lib/ldc/x86_64-linux-gnu/include/d/core/stdc/time.d(153):
Error: undefined identifier time_t, did you mean function time?
/usr/lib/ldc/x86_64-linux-gnu/include/d/core/stdc/time.d(153):
Error: undefined identifier tm
```