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.

llvm-svn: 200388
diff --git a/llvm/lib/Target/ARM/ARMSubtarget.h b/llvm/lib/Target/ARM/ARMSubtarget.h
index 3a9f940..200f198 100644
--- a/llvm/lib/Target/ARM/ARMSubtarget.h
+++ b/llvm/lib/Target/ARM/ARMSubtarget.h
@@ -328,6 +328,16 @@
            !isTargetDarwin();
   }
 
+  // ARM Targets that support EHABI exception handling standard
+  // Darwin uses SjLj. Other targets might need more checks.
+  bool isTargetEHABICompatible() const {
+    return (TargetTriple.getEnvironment() == Triple::EABI ||
+            TargetTriple.getEnvironment() == Triple::GNUEABI ||
+            TargetTriple.getEnvironment() == Triple::EABIHF ||
+            TargetTriple.getEnvironment() == Triple::GNUEABIHF) &&
+           !isTargetDarwin();
+  }
+
   bool isTargetHardFloat() const {
     return TargetTriple.getEnvironment() == Triple::GNUEABIHF ||
            TargetTriple.getEnvironment() == Triple::EABIHF;