Fix the CMake build

One part of this might change -- master contains some uses of
std::make_unique which Alexis might get rid of.

Change-Id: I40ae17f4e88920c4d60b79e1d4b117a7800fcd82
Reviewed-on: https://swiftshader-review.googlesource.com/c/23028
Reviewed-by: Alexis Hétu <sugoi@google.com>
Tested-by: Chris Forbes <chrisforbes@google.com>
diff --git a/src/Vulkan/VkCommandBuffer.cpp b/src/Vulkan/VkCommandBuffer.cpp
index 45f9199..dbcb386 100644
--- a/src/Vulkan/VkCommandBuffer.cpp
+++ b/src/Vulkan/VkCommandBuffer.cpp
@@ -14,6 +14,8 @@
 
 #include "VkCommandBuffer.hpp"
 
+#include <cstring>
+
 namespace vk
 {
 
@@ -524,4 +526,4 @@
 	state = EXECUTABLE;
 }
 
-} // namespace vk
\ No newline at end of file
+} // namespace vk