[SystemZ][z/OS] Fix warnings from unsigned int to long in 32-bit mode
This patch fixes the warnings which shows up when libcxx library started to be compiled in 32-bit mode on z/OS.
More specifically, the assignment from unsigned int to time_t aka long was flags as follows:
```
libcxx/include/c++/v1/__support/ibm/nanosleep.h:31:11: warning: implicit conversion changes signedness: 'unsigned int' to 'time_t' (aka 'long') [-Wsign-conversion]
__sec = sleep(static_cast<unsigned int>(__sec));
~ ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
libcxx/include/c++/v1/__support/ibm/nanosleep.h:36:36: warning: implicit conversion changes signedness: 'unsigned int' to 'long' [-Wsign-conversion]
__rem->tv_nsec = __micro_sec * 1000;
~ ~~~~~~~~~~~~^~~~~~
libcxx/include/c++/v1/__support/ibm/nanosleep.h:47:36: warning: implicit conversion changes signedness: 'unsigned int' to 'long' [-Wsign-conversion]
__rem->tv_nsec = __micro_sec * 1000;
~ ~~~~~~~~~~~~^~~~~~
3 warnings generated.
```
Here is a small test case illustrating the issue:
```
typedef long time_t ;
unsigned int sleep(unsigned int );
int main() {
time_t sec = 0;
#ifdef FIX
sec = static_cast<time_t>(sleep(static_cast<unsigned int>(sec)));
#else
sec = sleep(static_cast<unsigned int>(sec));
#endif
}
```
clang++ -c -Wsign-conversion -m32 t.C
```
t.C:8:9: warning: implicit conversion changes signedness: 'unsigned int' to 'time_t' (aka 'long') [-Wsign-conversion]
sec = sleep(static_cast<unsigned int>(sec));
~ ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Reviewed By: ldionne, #libc, Quuxplusone, Mordante
Differential Revision: https://reviews.llvm.org/D112837
GitOrigin-RevId: 422cf2b506c1240def78b9a5e5b7f32abbcff243
1 file changed
