upgrade gcc for travis build (#1995)

Author: gkorland

.travis.yml

@@ -1,7 +1,8 @@
-dist: xenial
+dist: trusty
 sudo: required
 language: java
 jdk:
+  - openjdk7
   - oraclejdk8
 before_install:
     - wget -O stunnel.tar.gz ftp://ftp.stunnel.org/stunnel/archive/5.x/stunnel-5.29.tar.gz

Makefile

@@ -340,8 +340,12 @@ release:
 	make stop
 
 travis-install:
-	g++ --version
-	sudo apt-get install -y build-essential
+	sudo add-apt-repository -y ppa:ubuntu-toolchain-r/test
+	sudo apt-get -y update
+	sudo apt-get install -y gcc-8 g++-8
+	cd /usr/bin ;\
+	sudo ln -sf gcc-8 gcc ;\
+	sudo ln -sf g++-8 g++
 	[ ! -e redis-git ] && git clone https://github.com/antirez/redis.git --branch unstable --single-branch redis-git || true
 	$(MAKE) -C redis-git clean
 	$(MAKE) -C redis-git