utils/genrandconfig: test configurations with BR2_PACKAGE_PYTHON3_PY_ONLY

Python3 variant of
https://git.buildroot.net/buildroot-test/commit/?id=c0de21d9530af53eae5588d99d90c7e0cb87c543

to support Kodi 19 which depends on python3:
https://git.buildroot.net/buildroot/commit/?id=148e695e37561fe45d4726cb68f6454464d17797

Signed-off-by: Bernd Kuhls <bernd.kuhls@t-online.de>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>

utils/genrandconfig

@@ -367,6 +367,8 @@ def gen_config(args):
         configlines.append("BR2_STATIC_LIBS=y\n")
     if randint(0, 20) == 0:
         configlines.append("BR2_PACKAGE_PYTHON_PY_ONLY=y\n")
+    if randint(0, 20) == 0:
+        configlines.append("BR2_PACKAGE_PYTHON3_PY_ONLY=y\n")
     if randint(0, 5) == 0:
         configlines.append("BR2_OPTIMIZE_2=y\n")
     if randint(0, 4) == 0: