[ubsan] Fix complaint in NewArray when size == 0

While strictly speaking it is legal (though useless) to dynamically
create zero-length arrays with "new T[0]", UBSan does not like it,
so this CL avoids doing it. It fixes the error:

../../src/allocation.h:41:34: runtime error: constructor call on
address 0x... with insufficient space for an object of type 'unsigned char'

Bug: v8:3770
Change-Id: I5017767c59df0d8928f7493f92d2d04519083964
Reviewed-on: https://chromium-review.googlesource.com/c/1356902Reviewed-by: Bill Budge <bbudge@chromium.org>
Commit-Queue: Jakob Kummerow <jkummerow@chromium.org>
Cr-Commit-Position: refs/heads/master@{#57984}

src/interface-descriptors.cc

@@ -15,6 +15,9 @@ void CallInterfaceDescriptorData::InitializePlatformSpecific(
 
   register_param_count_ = register_parameter_count;
 
+  // UBSan doesn't like creating zero-length arrays.
+  if (register_parameter_count == 0) return;
+
   // InterfaceDescriptor owns a copy of the registers array.
   register_params_ = NewArray<Register>(register_parameter_count, no_reg);
   for (int i = 0; i < register_parameter_count; i++) {

src/interface-descriptors.h

@@ -145,7 +145,8 @@ class V8_EXPORT_PRIVATE CallInterfaceDescriptorData {
  private:
   bool IsInitializedPlatformSpecific() const {
     const bool initialized =
-        register_param_count_ >= 0 && register_params_ != nullptr;
+        (register_param_count_ == 0 && register_params_ == nullptr) ||
+        (register_param_count_ > 0 && register_params_ != nullptr);
     // Platform-specific initialization happens before platform-independent.
     return initialized;
   }