[lld-macho] Fix compact unwind output for 32 bit builds

[DavidSpickett]

Summary

This test was failing on our 32 bit build bot:
https://lab.llvm.org/buildbot/#/builders/178/builds/2463

This happened because in UnwindInfoSectionImpl::finalize
a decision is made whether to write out regular or compressed
unwind info.

One check in this does:

if (cuPtr->functionAddress >= functionAddressMax) {
        break;

Where cuPtr->functionAddress was uint64_t and functionAddressMax
was uintptr_t, which is 4 bytes on a 32 bit system.

Using uint64_t for functionAddressMax fixes this problem.
Presumably because at only 4 bytes, the max is much lower than
we expect. We're targetting 64 bit though so the size of the max
should match the size of the addresses.

[int3]

Thank you!

lld/MachO/UnwindInfoSection.cpp

void UnwindInfoSectionImpl::finalize() {
   //     and 127..255 references a local per-second-level-page table.
   // First we try the compact format and determine how many entries fit.
   // If more entries fit in the regular format, we use that.
   for (size_t i = 0; i < cuIndices.size();) {
     size_t idx = cuIndices[i];
     secondLevelPages.emplace_back();
     SecondLevelPage &page = secondLevelPages.back();
     page.entryIndex = i;
-    uintptr_t functionAddressMax =
+    uint64_t functionAddressMax =
         cuEntries[idx].functionAddress + COMPRESSED_ENTRY_FUNC_OFFSET_MASK;
     size_t n = commonEncodings.size();
     size_t wordsRemaining =
         SECOND_LEVEL_PAGE_WORDS -
         sizeof(unwind_info_compressed_second_level_page_header) /
             sizeof(uint32_t);
     while (wordsRemaining >= 1 && i < cuIndices.size()) {
       idx = cuIndices[i];