[JITLink] Update DEBUG_TYPE string for llvm-jitlink.

Apparently LLVM_DEBUG doesn't like dashes in strings.
diff --git a/llvm/tools/llvm-jitlink/llvm-jitlink.cpp b/llvm/tools/llvm-jitlink/llvm-jitlink.cpp
index 7765d53..3f40f7d 100644
--- a/llvm/tools/llvm-jitlink/llvm-jitlink.cpp
+++ b/llvm/tools/llvm-jitlink/llvm-jitlink.cpp
@@ -40,7 +40,7 @@
 #include <list>
 #include <string>
 
-#define DEBUG_TYPE "llvm-jitlink"
+#define DEBUG_TYPE "llvm_jitlink"
 
 using namespace llvm;
 using namespace llvm::jitlink;