tests: skip va_list functions in testapi

Building on ARM or AArch with GCC was falling over as an int isn't a
va_list.

```
../testapi.c: In function ‘main’:
../testapi.c:546:34: error: incompatible type for argument 4 of ‘xmlStrVPrintf’
  546 |     xmlStrVPrintf(NULL, 0, NULL, 0);
      |                                  ^
      |                                  |
      |                                  int
In file included from ../include/libxml/tree.h:32,
                 from ../include/libxml/parser.h:20,
                 from ../include/libxml/HTMLparser.h:22,
                 from ../testapi.c:13:
../include/libxml/xmlstring.h:105:50: note: expected ‘va_list’ but argument is of type ‘int’
  105 |                                          va_list ap) LIBXML_ATTR_FORMAT(3,0);
      |                                          ~~~~~~~~^~
```
diff --git a/codegen/genTestApi.py b/codegen/genTestApi.py
index 07f9792..2805316 100755
--- a/codegen/genTestApi.py
+++ b/codegen/genTestApi.py
@@ -130,6 +130,22 @@
     'htmlReadFd': True,
     'xmlReadFd': True,
     'xmlReaderForFd': True,
+
+    # uses va_list
+    'xmlStrVPrintf': True,
+    'xmlTextWriterWriteVFormatAttribute': True,
+    'xmlTextWriterWriteVFormatAttributeNS': True,
+    'xmlTextWriterWriteVFormatCDATA': True,
+    'xmlTextWriterWriteVFormatComment': True,
+    'xmlTextWriterWriteVFormatDTD': True,
+    'xmlTextWriterWriteVFormatDTDAttlist': True,
+    'xmlTextWriterWriteVFormatDTDElement': True,
+    'xmlTextWriterWriteVFormatDTDInternalEntity': True,
+    'xmlTextWriterWriteVFormatElement': True,
+    'xmlTextWriterWriteVFormatElementNS': True,
+    'xmlTextWriterWriteVFormatPI': True,
+    'xmlTextWriterWriteVFormatRaw': True,
+    'xmlTextWriterWriteVFormatString': True,
 }
 
 # Parse document
diff --git a/testapi.c b/testapi.c
index 76d4d16..6ed0c38 100644
--- a/testapi.c
+++ b/testapi.c
@@ -543,7 +543,6 @@
     xmlStrEqual(NULL, NULL);
     xmlStrPrintf(NULL, 0, NULL, 0);
     xmlStrQEqual(NULL, NULL, NULL);
-    xmlStrVPrintf(NULL, 0, NULL, 0);
     xmlStrcasecmp(NULL, NULL);
     xmlStrcasestr(NULL, NULL);
     xmlFree(xmlStrcat(NULL, NULL));
@@ -1198,19 +1197,6 @@
     xmlTextWriterWriteRaw(NULL, NULL);
     xmlTextWriterWriteRawLen(NULL, NULL, 0);
     xmlTextWriterWriteString(NULL, NULL);
-    xmlTextWriterWriteVFormatAttribute(NULL, NULL, NULL, 0);
-    xmlTextWriterWriteVFormatAttributeNS(NULL, NULL, NULL, NULL, NULL, 0);
-    xmlTextWriterWriteVFormatCDATA(NULL, NULL, 0);
-    xmlTextWriterWriteVFormatComment(NULL, NULL, 0);
-    xmlTextWriterWriteVFormatDTD(NULL, NULL, NULL, NULL, NULL, 0);
-    xmlTextWriterWriteVFormatDTDAttlist(NULL, NULL, NULL, 0);
-    xmlTextWriterWriteVFormatDTDElement(NULL, NULL, NULL, 0);
-    xmlTextWriterWriteVFormatDTDInternalEntity(NULL, 0, NULL, NULL, 0);
-    xmlTextWriterWriteVFormatElement(NULL, NULL, NULL, 0);
-    xmlTextWriterWriteVFormatElementNS(NULL, NULL, NULL, NULL, NULL, 0);
-    xmlTextWriterWriteVFormatPI(NULL, NULL, NULL, 0);
-    xmlTextWriterWriteVFormatRaw(NULL, NULL, 0);
-    xmlTextWriterWriteVFormatString(NULL, NULL, 0);
 #endif /* LIBXML_WRITER_ENABLED */
 
 #ifdef LIBXML_XINCLUDE_ENABLED