Provide CC_MD5 on OS X < 10.5.

--- ld64-241.9/src/ld/OutputFile.cpp	2015-01-22 23:20:33.000000000 +0100
+++ ld64-241.9/src/ld/OutputFile.cpp	2015-01-22 23:26:02.000000000 +0100
@@ -71,6 +71,19 @@
 #include "LinkEdit.hpp"
 #include "LinkEditClassic.hpp"
 
+#if MAC_OS_X_VERSION_MIN_REQUIRED < 1050
+/* CC_MD5 missing on < 10.5 - provide replacement */
+unsigned char *CC_MD5(const void *data, CC_LONG len, unsigned char *md) {
+	CC_MD5_CTX ctx;
+	if(md == NULL)
+		return NULL;
+
+	CC_MD5_Init(&ctx);
+	CC_MD5_Update(&ctx, data, len);
+	CC_MD5_Final(md, &ctx);
+	return md;
+}
+#endif
 
 namespace ld {
 namespace tool {