[msan] Change track-origins default mode from 1 to 2.

Change -fsanitize-memory-track-origins to be equivalent to
-fsanitize-memory-track-origins=2.

Track-origins=2 provides a lot more detailed reports at the cost of
some additional slowdown (ranging from none to, sometimes, 3x; ~3% average on
SPEC2006).

llvm-svn: 230644
diff --git a/clang/lib/Driver/SanitizerArgs.cpp b/clang/lib/Driver/SanitizerArgs.cpp
index 0488abc..11b9288 100644
--- a/clang/lib/Driver/SanitizerArgs.cpp
+++ b/clang/lib/Driver/SanitizerArgs.cpp
@@ -360,7 +360,7 @@
                             options::OPT_fsanitize_memory_track_origins,
                             options::OPT_fno_sanitize_memory_track_origins)) {
       if (A->getOption().matches(options::OPT_fsanitize_memory_track_origins)) {
-        MsanTrackOrigins = 1;
+        MsanTrackOrigins = 2;
       } else if (A->getOption().matches(
                      options::OPT_fno_sanitize_memory_track_origins)) {
         MsanTrackOrigins = 0;