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

runtime/platform/address_sanitizer.h

Index: runtime/platform/address_sanitizer.h
diff --git a/runtime/platform/address_sanitizer.h b/runtime/platform/address_sanitizer.h
index 584f3a523952bf15746ecce0917b865d91ec99ca..ec8baf70d1bbee46340d52a78ada7677175b103a 100644
--- a/runtime/platform/address_sanitizer.h
+++ b/runtime/platform/address_sanitizer.h
@@ -11,13 +11,17 @@
 // told about areas where the VM does the equivalent of a long-jump.
 #if defined(__has_feature)
 #if __has_feature(address_sanitizer)
-extern "C" void __asan_unpoison_memory_region(void *, size_t);
+extern "C" void __asan_unpoison_memory_region(void*, size_t);
 #define ASAN_UNPOISON(ptr, len) __asan_unpoison_memory_region(ptr, len)
 #else  // __has_feature(address_sanitizer)
-#define ASAN_UNPOISON(ptr, len) do {} while (false && (ptr) == 0 && (len) == 0)
+#define ASAN_UNPOISON(ptr, len)                                                \
+  do {                                                                         \
+  } while (false && (ptr) == 0 && (len) == 0)
 #endif  // __has_feature(address_sanitizer)
-#else  // defined(__has_feature)
-#define ASAN_UNPOISON(ptr, len) do {} while (false && (ptr) == 0 && (len) == 0)
+#else   // defined(__has_feature)
+#define ASAN_UNPOISON(ptr, len)                                                \
+  do {                                                                         \
+  } while (false && (ptr) == 0 && (len) == 0)
 #endif  // defined(__has_feature)
 
 #endif  // RUNTIME_PLATFORM_ADDRESS_SANITIZER_H_