[vm] Adjust MSAN compile flags to match google3 to reproduce MSAN error in the regexp interpreter.

TEST=msan
Bug: b/489355669
Change-Id: I3ade526a67e5e7d95c8d8862eb92924337057d94
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/485240
Commit-Queue: Ryan Macnak <rmacnak@google.com>
Reviewed-by: Slava Egorov <vegorov@google.com>

build/config/compiler/BUILD.gn

@@ -156,7 +156,16 @@ config("compiler") {
       ldflags += [ "-fsanitize=leak" ]
     }
     if (is_msan) {
-      cflags += [ "-fsanitize=memory" ]
+      cflags += [
+        "-fsanitize=memory",
+
+        # Matching the google3 settings. Whether MSAN reports a use of an
+        # uninitialized value is sensitive to inlining.
+        "-mllvm",
+        "-inline-instr-cost=20",
+        "-mllvm",
+        "-inline-memaccess-cost=20",
+      ]
       ldflags += [ "-fsanitize=memory" ]
     }
     if (is_tsan) {