Fix a -Wbitwise-conditional-parentheses warning in _LIBUNWIND_ARM_EHABI libunwind builds

[thakis]

Summary

src/UnwindCursor.hpp:1344:51: error: operator '?:' has lower precedence than '|';
    '|' will be evaluated first [-Werror,-Wbitwise-conditional-parentheses]
  _info.flags = isSingleWordEHT ? 1 : 0 | scope32 ? 0x2 : 0;  // Use enum?
                                      ~~~~~~~~~~~ ^
src/UnwindCursor.hpp:1344:51: note: place parentheses around the '|' expression
    to silence this warning
  _info.flags = isSingleWordEHT ? 1 : 0 | scope32 ? 0x2 : 0;  // Use enum?
                                                  ^
                                      (          )
src/UnwindCursor.hpp:1344:51: note: place parentheses around the '?:' expression
    to evaluate it first
  _info.flags = isSingleWordEHT ? 1 : 0 | scope32 ? 0x2 : 0;  // Use enum?
                                                  ^
                                          (                )

But 0 | is a no-op for either of those two interpretations, so I think what was meant here was

_info.flags = (isSingleWordEHT ? 1 : 0) | (scope32 ? 0x2 : 0);  // Use enum?

Previously, if isSingleWordEHT was set, bit 2 would never be set. Now it is. From what I can tell, the only thing that checks these bitmask is ProcessDescriptors in Unwind-EHABI.cpp, and that only cares about bit 1, so in practice this shouldn't have much of an effect.

[thakis]

Useful resources for reading the old ehabi code:

• Original code: https://reviews.llvm.org/rL211743
• EHABI spec: https://static.docs.arm.com/ihi0038/a/IHI0038A_ehabi.pdf?_ga=2.135617969.1216612656.1580737833-1865674396.1580737769

[hans]

Pushed to 10.x as 8de07c31c1aafa848f515d721e6cf065a0701e81

libunwind/src/UnwindCursor.hpp

if (indexDataAddr == 0)
     return false;
 
   uint32_t indexData = _addressSpace.get32(indexDataAddr);
   if (indexData == UNW_EXIDX_CANTUNWIND)
     return false;
 
   // If the high bit is set, the exception handling table entry is inline inside
   // the index table entry on the second word (aka |indexDataAddr|). Otherwise,
-  // the table points at an offset in the exception handling table (section 5 EHABI).
+  // the table points at an offset in the exception handling table (section 5
+  // EHABI).
   pint_t exceptionTableAddr;
   uint32_t exceptionTableData;
   bool isSingleWordEHT;
   if (indexData & 0x80000000) {
     exceptionTableAddr = indexDataAddr;
     // TODO(ajwong): Should this data be 0?
     exceptionTableData = indexData;
     isSingleWordEHT = true;
bool UnwindCursor<A, R>::getInfoFromEHABISection(
   }
 
   _info.start_ip = thisPC;
   _info.end_ip = nextPC;
   _info.handler = personalityRoutine;
   _info.unwind_info = exceptionTableAddr;
   _info.lsda = lsda;
   // flags is pr_cache.additional. See EHABI #7.2 for definition of bit 0.
-  _info.flags = isSingleWordEHT ? 1 : 0 | scope32 ? 0x2 : 0;  // Use enum?
+  _info.flags = (isSingleWordEHT ? 1 : 0) | (scope32 ? 0x2 : 0);  // Use enum?
 
   return true;
 }
 #endif
 
 #if defined(_LIBUNWIND_SUPPORT_DWARF_UNWIND)
 template <typename A, typename R>
 bool UnwindCursor<A, R>::getInfoFromDwarfSection(pint_t pc,