Add support for the OpenBSD for Bitrig.

Patch by David Hill.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@161344 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/tools/llvm-shlib/Makefile b/tools/llvm-shlib/Makefile
index 75bee07..6d6c6e9 100644
--- a/tools/llvm-shlib/Makefile
+++ b/tools/llvm-shlib/Makefile
@@ -63,7 +63,7 @@
     endif
 endif
 
-ifeq ($(HOST_OS), $(filter $(HOST_OS), Linux FreeBSD OpenBSD GNU))
+ifeq ($(HOST_OS), $(filter $(HOST_OS), Linux FreeBSD OpenBSD GNU Bitrig))
     # Include everything from the .a's into the shared library.
     LLVMLibsOptions := -Wl,--whole-archive $(LLVMLibsOptions) \
                        -Wl,--no-whole-archive