Use the target triple from the target machine rather than the module

to determine whether or not we're on a darwin platform for debug code
emitting.

Solves the problem of a module with no triple on the command line
and no triple in the module using non-gdb ok features on darwin. Fix
up the member-pointers test to check the correct things for cross
platform (DW_FORM_flag is a good prefix).

Unfortunately no testcase because I have no ideas how to test something
without a triple and without a triple in the module yet check
precisely on two platforms. Ideas welcome.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@180660 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/CodeGen/AsmPrinter.h

@@ -135,6 +135,9 @@ namespace llvm {
     /// getDataLayout - Return information about data layout.
     const DataLayout &getDataLayout() const;
 
+    /// getTargetTriple - Return the target triple string.
+    StringRef getTargetTriple() const;
+
     /// getCurrentSection() - Return the current section we are emitting to.
     const MCSection *getCurrentSection() const;