[LLD] [MachO] Fix GCC build warnings

This fixes the following warnings produced by GCC 9:

    ../tools/lld/MachO/Arch/ARM64.cpp: In member function ‘void {anonymous}::OptimizationHintContext::applyAdrpLdr(const lld::macho::OptimizationHint&)’:
    ../tools/lld/MachO/Arch/ARM64.cpp:448:18: warning: comparison of integer expressions of different signedness: ‘int64_t’ {aka ‘long int’} and ‘uint64_t’ {aka ‘long unsigned int’} [-Wsign-compare]
      448 |   if (ldr.offset != (rel1->referentVA & 0xfff))
          |       ~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    ../tools/lld/MachO/UnwindInfoSection.cpp: In function ‘bool canFoldEncoding(compact_unwind_encoding_t)’:
    ../tools/lld/MachO/UnwindInfoSection.cpp:404:44: warning: comparison between ‘enum<unnamed>’ and ‘enum<unnamed>’ [-Wenum-compare]
      404 |   static_assert(UNWIND_X86_64_MODE_MASK == UNWIND_X86_MODE_MASK, "");
          |                                            ^~~~~~~~~~~~~~~~~~~~
    ../tools/lld/MachO/UnwindInfoSection.cpp:405:49: warning: comparison between ‘enum<unnamed>’ and ‘enum<unnamed>’ [-Wenum-compare]
      405 |   static_assert(UNWIND_X86_64_MODE_STACK_IND == UNWIND_X86_MODE_STACK_IND, "");
          |                                                 ^~~~~~~~~~~~~~~~~~~~~~~~~

Differential Revision: https://reviews.llvm.org/D130970

Author: mstorsjo

lld/MachO/Arch/ARM64.cpp

@@ -445,7 +445,7 @@ void OptimizationHintContext::applyAdrpLdr(const OptimizationHint &hint) {
   Optional<PerformedReloc> rel2 = findReloc(hint.offset0 + hint.delta[0]);
   if (!rel1 || !rel2)
     return;
-  if (ldr.offset != (rel1->referentVA & 0xfff))
+  if (ldr.offset != static_cast<int64_t>(rel1->referentVA & 0xfff))
     return;
   ldr.offset = rel1->referentVA - rel2->rel.offset - isec->getVA();
   if (!isLiteralLdrEligible(ldr))

lld/MachO/UnwindInfoSection.cpp

@@ -401,8 +401,12 @@ static bool canFoldEncoding(compact_unwind_encoding_t encoding) {
   // of the unwind info's unwind address, two functions that have identical
   // unwind info can't be folded if it's using this encoding since both
   // entries need unique addresses.
-  static_assert(UNWIND_X86_64_MODE_MASK == UNWIND_X86_MODE_MASK, "");
-  static_assert(UNWIND_X86_64_MODE_STACK_IND == UNWIND_X86_MODE_STACK_IND, "");
+  static_assert(static_cast<uint32_t>(UNWIND_X86_64_MODE_MASK) ==
+                    static_cast<uint32_t>(UNWIND_X86_MODE_MASK),
+                "");
+  static_assert(static_cast<uint32_t>(UNWIND_X86_64_MODE_STACK_IND) ==
+                    static_cast<uint32_t>(UNWIND_X86_MODE_STACK_IND),
+                "");
   if ((target->cpuType == CPU_TYPE_X86_64 || target->cpuType == CPU_TYPE_X86) &&
       (encoding & UNWIND_X86_64_MODE_MASK) == UNWIND_X86_64_MODE_STACK_IND) {
     // FIXME: Consider passing in the two function addresses and getting