posix.cfg: Add configuration for function gai_strerror()

Reference:
https://pubs.opengroup.org/onlinepubs/9699919799/functions/gai_strerror.html

cfg/posix.cfg

@@ -2822,6 +2822,17 @@ The function 'mktemp' is considered to be dangerous due to race conditions and s
       <not-bool/>
     </arg>
   </function>
+  <!-- const char *gai_strerror(int ecode); -->
+  <function name="gai_strerror">
+    <noreturn>false</noreturn>
+    <returnValue type="const char *"/>
+    <use-retval/>
+    <leak-ignore/>
+    <arg nr="1" direction="in">
+      <not-uninit/>
+      <not-bool/>
+    </arg>
+  </function>
   <!-- void endhostent(void); -->
   <function name="endhostent">
     <noreturn>false</noreturn>