Fix travis for out of repo prs

.travis.yml

@@ -17,7 +17,7 @@ services:
 before_install:
   - sed -i 's/git@github.com:/https:\/\/github.com\//' .gitmodules
   - git submodule update --init --recursive
-  - openssl aes-256-cbc -K $encrypted_c158cd588669_key -iv $encrypted_c158cd588669_iv -in keystore.p12.enc -out keystore.p12 -d
+  - ./scripts/ci/setup_signing_key.sh
 
 script:
   - export QFIELD_SDK_VERSION=$(awk -F "=" '/osgeo4a_version/{print $2}' sdk.conf)

scripts/ci/setup_signing_key.sh

@@ -0,0 +1,6 @@
+#!/bin/bash
+set -e
+
+if [[ ${TRAVIS_SECURE_ENV_VARS} = true ]]; then
+  openssl aes-256-cbc -K $encrypted_c158cd588669_key -iv $encrypted_c158cd588669_iv -in keystore.p12.enc -out keystore.p12 -d
+fi