[BOLT][NFC] Remove text section assertion

[maksfb]

Summary

We can emit a binary without a new text section. Hence, the text section
assertion is not needed.

[rafauler]

LGTM

bolt/lib/Rewrite/RewriteInstance.cpp

std::vector<BinarySection *> RewriteInstance::getCodeSections() {
   // Determine the order of sections.
   llvm::stable_sort(CodeSections, compareSections);
 
   return CodeSections;
 }
 
 void RewriteInstance::mapCodeSections(RuntimeDyld &RTDyld) {
   if (BC->HasRelocations) {
-    ErrorOr<BinarySection &> TextSection =
-        BC->getUniqueSectionByName(BC->getMainCodeSectionName());
-    assert(TextSection && ".text section not found in output");
-    assert(TextSection->hasValidSectionID() && ".text section should be valid");
-
     // Map sections for functions with pre-assigned addresses.
     for (BinaryFunction *InjectedFunction : BC->getInjectedBinaryFunctions()) {
       const uint64_t OutputAddress = InjectedFunction->getOutputAddress();
       if (!OutputAddress)
         continue;
 
       ErrorOr<BinarySection &> FunctionSection =
           InjectedFunction->getCodeSection();
if (BC->HasRelocations) {
     auto allocateAt = [&](uint64_t Address) {
       for (BinarySection *Section : CodeSections) {
         Address = alignTo(Address, Section->getAlignment());
         Section->setOutputAddress(Address);
         Address += Section->getOutputSize();
       }
 
       // Make sure we allocate enough space for huge pages.
-      if (opts::HotText) {
+      ErrorOr<BinarySection &> TextSection =
+          BC->getUniqueSectionByName(BC->getMainCodeSectionName());
+      if (opts::HotText && TextSection && TextSection->hasValidSectionID()) {
         uint64_t HotTextEnd =
             TextSection->getOutputAddress() + TextSection->getOutputSize();
         HotTextEnd = alignTo(HotTextEnd, BC->PageAlign);
         if (HotTextEnd > Address) {
           PaddingSize = HotTextEnd - Address;
           Address = HotTextEnd;
         }
       }