Fix x86 truncation warning in offset_range.pass.cpp.

offset_range.pass.cpp(49): warning C4244: 'initializing': conversion from 'const _Ty' to 'size_t', possible loss of data

std::min() is returning std::streamoff, which was being unnecessarily narrowed to std::size_t.

Author: StephanTLavavej

libcxx/test/std/input.output/file.streams/fstreams/ifstream.members/offset_range.pass.cpp

@@ -46,7 +46,7 @@ void test_tellg(std::streamoff total_size) {
     ofs.open(p, std::ios::out | std::ios::binary);
     assert(ofs.is_open());
     for (std::streamoff size = 0; size < total_size;) {
-      std::size_t n = std::min(static_cast<std::streamoff>(data.size()), total_size - size);
+      std::streamoff n = std::min(static_cast<std::streamoff>(data.size()), total_size - size);
       ofs.write(data.data(), n);
       size += n;
     }