AsmPrinter: Fix wrong OS X versions being emitted for darwin triples

The version numbers of the darwin kernel are different from the version
numbers of OS X, so we need adjustments if we had "*-*-darwin" triples.
Use the existing utility functions in TargetTriple for this.

Fixes rdar://22056966

Differential Revision: http://reviews.llvm.org/D14601

llvm-svn: 257555
diff --git a/llvm/test/CodeGen/X86/version_directive.ll b/llvm/test/CodeGen/X86/version_directive.ll
new file mode 100644
index 0000000..8e4e6dc
--- /dev/null
+++ b/llvm/test/CodeGen/X86/version_directive.ll
@@ -0,0 +1,4 @@
+; RUN: llc -mtriple x86_64-apple-darwin15.0.0 -o - /dev/null | FileCheck %s
+; RUN: llc -mtriple x86_64-apple-macosx10.11.0 -o - /dev/null | FileCheck %s
+
+; CHECK: .macosx_version_min 10, 11