CI: travis-ci: skip pcre2 on arm64 build

currently arm64 stuck with some error related to pcre2. while we beleive
pcre2 is not related to error itself, we can try not to install it
diff --git a/.travis.yml b/.travis.yml
index 0d72687..59f3450 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -48,6 +48,10 @@
     if: type == push
     compiler: clang
     env: TARGET=linux-glibc OPENSSL_VERSION=1.1.1f CC=clang-9
+    addons:
+      apt:
+        update: true
+        packages: [ liblua5.3-dev, libsystemd-dev, clang-9, socat ]
   - os: linux
     arch: s390x
     if: type == push