Add .clang-format and run clang-format on runtime/platform.

runtime/platform/memory_sanitizer.h

Index: runtime/platform/memory_sanitizer.h
diff --git a/runtime/platform/memory_sanitizer.h b/runtime/platform/memory_sanitizer.h
index dddfe31135298c515ea1495fd03aee257de621a4..27cb25d4b40b9f6a743e6873ab409a19024817a7 100644
--- a/runtime/platform/memory_sanitizer.h
+++ b/runtime/platform/memory_sanitizer.h
@@ -11,15 +11,19 @@
 // told about areas that are initialized by generated code.
 #if defined(__has_feature)
 #if __has_feature(memory_sanitizer)
-extern "C" void __msan_unpoison(void *, size_t);
+extern "C" void __msan_unpoison(void*, size_t);
 #define MSAN_UNPOISON(ptr, len) __msan_unpoison(ptr, len)
 #define NO_SANITIZE_MEMORY __attribute__((no_sanitize_memory))
 #else  // __has_feature(memory_sanitizer)
-#define MSAN_UNPOISON(ptr, len) do {} while (false && (ptr) == 0 && (len) == 0)
+#define MSAN_UNPOISON(ptr, len)                                                \
+  do {                                                                         \
+  } while (false && (ptr) == 0 && (len) == 0)
 #define NO_SANITIZE_MEMORY
 #endif  // __has_feature(memory_sanitizer)
-#else  // defined(__has_feature)
-#define MSAN_UNPOISON(ptr, len) do {} while (false && (ptr) == 0 && (len) == 0)
+#else   // defined(__has_feature)
+#define MSAN_UNPOISON(ptr, len)                                                \
+  do {                                                                         \
+  } while (false && (ptr) == 0 && (len) == 0)
 #define NO_SANITIZE_MEMORY
 #endif  // defined(__has_feature)