use mktmp so tmp file is not static

_integration-test/custom-ca-roots/setup.sh

@@ -25,8 +25,12 @@ openssl req -new -nodes -newkey rsa:2048 -keyout $TEST_NGINX_CONF_PATH/self.test
 
 # openssl req -in nginx/self.test.req -text -noout
 
+# Store extension details in a temporary file since python subprocess can't use process substitution
+temp_file=$(mktemp)
+printf "subjectAltName=DNS:self.test" >"$temp_file"
+
 openssl x509 -req -in $TEST_NGINX_CONF_PATH/self.test.req -CA $TEST_NGINX_CONF_PATH/ca.crt -CAkey $TEST_NGINX_CONF_PATH/ca.key \
- -addext "subjectAltName=DNS:self.test" \
+ -extfile "$temp_file" \
  -CAcreateserial -out $TEST_NGINX_CONF_PATH/self.test.crt -days 1 -sha256
 
 # openssl x509 -in nginx/self.test.crt -text -noout