Try and get snapshots running again

Author: gsherwood

.travis.yml

@@ -24,9 +24,17 @@ matrix:
       env: PHPUNIT_INCOMPAT=1
     - php: "7.4snapshot"
       env: PHPSTAN=1 PHPUNIT_INCOMPAT=1
+      addons:
+        apt:
+          packages:
+            - libonig-dev
     # Nightly is PHP 8.0 since Feb 2019.
     - php: nightly
       env: PHPUNIT_INCOMPAT=1
+      addons:
+        apt:
+          packages:
+            - libonig-dev
 
   allow_failures:
     - php: "7.4snapshot"