Define __ELF__ on FreeBSD. Patch by Roman Divacky!

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@64557 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Basic/Targets.cpp b/lib/Basic/Targets.cpp
index b37939f..ad7d6d5 100644
--- a/lib/Basic/Targets.cpp
+++ b/lib/Basic/Targets.cpp
@@ -58,7 +58,7 @@
   Define(Defs, "__FreeBSD_cc_version", version);
   Define(Defs, "__KPRINTF_ATTRIBUTE__");
   Define(Defs, "unix");
-  Define(Defs, "bsd");
+  Define(Defs, "__ELF__", "1");
   if (is64Bit) {
     Define(Defs, "__LP64__");
   }