gnu.cfg: Add configuration for __builtin_memcpy()

In case there is something like `#define memcpy __builtin_memcpy` in the
code our define for __builtin_memcpy does not work.
So the configuration for __builtin_memcpy is added as a fallback.

cfg/gnu.cfg

@@ -58,6 +58,27 @@
       <valid>0:</valid>
     </arg>
   </function>
+  <!-- void * __builtin_memcpy(void *dest, const void *source, size_t size);-->
+  <!-- memcpy() is sometimes defined as __builtin_memcpy() so the define above does not work -->
+  <function name="__builtin_memcpy">
+    <noreturn>false</noreturn>
+    <returnValue type="void *"/>
+    <leak-ignore/>
+    <arg nr="1" direction="out">
+      <not-null/>
+      <minsize type="argvalue" arg="3"/>
+    </arg>
+    <arg nr="2" direction="in">
+      <not-null/>
+      <not-uninit/>
+      <minsize type="argvalue" arg="3"/>
+    </arg>
+    <arg nr="3" direction="in">
+      <not-uninit/>
+      <not-bool/>
+      <valid>0:</valid>
+    </arg>
+  </function>
   <!-- void __builtin_prefetch (const void *addr, ...) -->
   <function name="__builtin_prefetch">
     <noreturn>false</noreturn>