[lld/mac] Add a few TimeTraceScopes

Identical literal folding takes ~1.4% of the time, and was missing
from the trace.

Signature computation still needs ~2.2% of the time, so probably worth
explicitly marking its contribution to "Write output file" (9.1%)

Differential Revision: https://reviews.llvm.org/D128343

lld/MachO/Driver.cpp

@@ -1073,6 +1073,7 @@ static void gatherInputSections() {
 }
 
 static void foldIdenticalLiterals() {
+  TimeTraceScope timeScope("Fold identical literals");
   // We always create a cStringSection, regardless of whether dedupLiterals is
   // true. If it isn't, we simply create a non-deduplicating CStringSection.
   // Either way, we must unconditionally finalize it here.

lld/MachO/ICF.cpp

@@ -373,6 +373,7 @@ void macho::markSymAsAddrSig(Symbol *s) {
 }
 
 void macho::markAddrSigSymbols() {
+  TimeTraceScope timeScope("Mark addrsig symbols");
   for (InputFile *file : inputFiles) {
     ObjFile *obj = dyn_cast<ObjFile>(file);
     if (!obj)

lld/MachO/Writer.cpp

@@ -1126,8 +1126,10 @@ void Writer::writeUuid() {
 }
 
 void Writer::writeCodeSignature() {
-  if (codeSignatureSection)
+  if (codeSignatureSection) {
+    TimeTraceScope timeScope("Write code signature");
     codeSignatureSection->writeHashes(buffer->getBufferStart());
+  }
 }
 
 void Writer::writeOutputFile() {