Replace @truncate with @intcast

This should be safe because `uid_t` will be 32-bit.

lib/std/os/linux.zig

@@ -745,33 +745,33 @@ pub fn setregid(rgid: gid_t, egid: gid_t) usize {
 
 pub fn getuid() uid_t {
     if (@hasField(SYS, "getuid32")) {
-        return @truncate(uid_t, syscall0(.getuid32));
+        return @intCast(uid_t, syscall0(.getuid32));
     } else {
-        return @truncate(uid_t, syscall0(.getuid));
+        return @intCast(uid_t, syscall0(.getuid));
     }
 }
 
 pub fn getgid() gid_t {
     if (@hasField(SYS, "getgid32")) {
-        return @truncate(gid_t, syscall0(.getgid32));
+        return @intCast(gid_t, syscall0(.getgid32));
     } else {
-        return @truncate(gid_t, syscall0(.getgid));
+        return @intCast(gid_t, syscall0(.getgid));
     }
 }
 
 pub fn geteuid() uid_t {
     if (@hasField(SYS, "geteuid32")) {
-        return @truncate(uid_t, syscall0(.geteuid32));
+        return @intCast(uid_t, syscall0(.geteuid32));
     } else {
-        return @truncate(uid_t, syscall0(.geteuid));
+        return @intCast(uid_t, syscall0(.geteuid));
     }
 }
 
 pub fn getegid() gid_t {
     if (@hasField(SYS, "getegid32")) {
-        return @truncate(gid_t, syscall0(.getegid32));
+        return @intCast(gid_t, syscall0(.getegid32));
     } else {
-        return @truncate(gid_t, syscall0(.getegid));
+        return @intCast(gid_t, syscall0(.getegid));
     }
 }