fix add_100_millis handle different time types

Author: dvdsk

src/tools/miri/tests/pass-dep/libc/libc-time.rs

@@ -358,10 +358,12 @@ mod test_clock_nanosleep {
 
     /// Helper function used to create an instant in the future
     fn add_100_millis(mut ts: libc::timespec) -> libc::timespec {
-        const SECOND: i64 = 1_000_000_000;
+        // While tv_nsec has type `c_long` tv_sec has type `time_t`. These might
+        // end up as different types (for example: like i32 and i64).
+        const SECOND: libc::c_long = 1_000_000_000;
         ts.tv_nsec += SECOND / 10;
         // If this pushes tv_nsec to SECOND or higher, we need to overflow to tv_sec.
-        ts.tv_sec += ts.tv_nsec / SECOND;
+        ts.tv_sec += (ts.tv_nsec / SECOND) as libc::time_t;
         ts.tv_nsec %= SECOND;
         ts
     }
@@ -427,4 +429,3 @@ mod test_clock_nanosleep {
         assert!(start_test_sleep.elapsed() > Duration::from_millis(100));
     }
 }
-