Enable EHABI by default

After all hard work to implement the EHABI and with the test-suite
passing, it's time to turn it on by default and allow users to
disable it as a work-around while we fix the eventual bugs that show
up.

This commit also remove the -arm-enable-ehabi-descriptors, since we
want the tables to be printed every time the EHABI is turned on
for non-Darwin ARM targets.

Although MCJIT EHABI is not working yet (needs linking with the right
libraries), this commit also fixes some relocations on MCJIT regarding
the EH tables/lib calls, and update some tests to avoid using EH tables
when none are needed.

The EH tests in the test-suite that were previously disabled on ARM
now pass with these changes, so a follow-up commit on the test-suite
will re-enable them.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@200388 91177308-0d34-0410-b5e6-96231b3b80d8

lib/ExecutionEngine/RuntimeDyld/RuntimeDyldELF.cpp

@@ -481,8 +481,11 @@ void RuntimeDyldELF::resolveARMRelocation(const SectionEntry &Section,
   default:
     llvm_unreachable("Not implemented relocation type!");
 
+  case ELF::R_ARM_NONE:
+    break;
   // Write a 32bit value to relocation address, taking into account the
   // implicit addend encoded in the target.
+  case ELF::R_ARM_PREL31:
   case ELF::R_ARM_TARGET1:
   case ELF::R_ARM_ABS32:
     *TargetPtr = *Placeholder + Value;