fix arm cache

.travis.yml

@@ -60,10 +60,6 @@ matrix:
       name: "Linux ARM64 Bionic"
       language: bash
       filter_secrets: false
-      addons:
-        apt:
-          packages:
-            - ruby
       env:
         - GAMOS=linux
         - PLATFORM=arm64

src/travis/linux-arm64-before-install.sh

@@ -25,6 +25,7 @@ if [ $SSLRESULT -ne 0 ] || [[ "$SSLVER" != "OpenSSL $BUILD_OPENSSL_VERSION "* ]]
   sudo apt-get -qq --yes update > /dev/null
   sudo apt-get -qq --yes build-dep python3 > /dev/null
   sudo apt-get -qq --yes install zlib1g-dev > /dev/null
+  sudo apt-get -qq --yes install libffi-dev > /dev/null
 
   # Compile latest OpenSSL
   echo "Downloading OpenSSL..."