[libunwind] Fix libunwind build without a heap

[Amanieu]

Summary

This patch adds a missing guard for _LIBUNWIND_NO_HEAP around code dealing with the .cfi_remember_state and .cfi_restore_state instructions.

[compnerd]

Please upload patches with complete context (diff -u9999).

[compnerd]

Do you have commit access or do you need someone to commit this on your behalf?

[Amanieu]

Added context

[Amanieu]

Please commit on my behalf.

[compnerd]

rGb31cb3aa5ee7ea92d830b06a0a7e42c7f2791dd4

libunwind/src/DwarfParser.hpp

bool CFI_Parser<A>::parseFDEInstructions(A &addressSpace,
   bool returnValue =
       parseInstructions(addressSpace, cieInfo.cieInstructions,
                         cieInfo.cieStart + cieInfo.cieLength, cieInfo,
                         (pint_t)(-1), rememberStack, arch, results) &&
       parseInstructions(addressSpace, fdeInfo.fdeInstructions,
                         fdeInfo.fdeStart + fdeInfo.fdeLength, cieInfo,
                         upToPC - fdeInfo.pcStart, rememberStack, arch, results);
 
+#if !defined(_LIBUNWIND_NO_HEAP)
   // Clean up rememberStack. Even in the case where every DW_CFA_remember_state
   // is paired with a DW_CFA_restore_state, parseInstructions can skip restore
   // opcodes if it reaches the target PC and stops interpreting, so we have to
   // make sure we don't leak memory.
   while (rememberStack) {
     PrologInfoStackEntry *next = rememberStack->next;
     free(rememberStack);
     rememberStack = next;
   }
+#endif
 
   return returnValue;
 }
 
 /// "run" the DWARF instructions
 template <typename A>
 bool CFI_Parser<A>::parseInstructions(A &addressSpace, pint_t instructions,
                                       pint_t instructionsEnd,