Update Travis CI to Ubuntu Xenial

This updates to Qt 5.12, since Stephan has a build for that in his
PPA. But we need to turn off RDRNAD support for the Valgrind build, as
it doesn't understand that instruction.

This also downgrades GCC to 5.4, which is what comes by default with
Travis CI.

Signed-off-by: Thiago Macieira <[email protected]>

Author: thiagomacieira

.travis.yml

@@ -2,45 +2,46 @@ language: cpp
 matrix:
   include:
     - os: linux
+      dist: xenial
       addons:
         apt:
           sources:
-            - ubuntu-toolchain-r-test
-            - sourceline: 'ppa:beineri/opt-qt596-trusty'
+            - sourceline: 'ppa:beineri/opt-qt-5.12.1-xenial'
           packages:
-            - qt59base valgrind
-            - g++-7
+            - qt512base valgrind
             - doxygen
       env:
         - QMAKESPEC=linux-g++
-        - EVAL="CC=gcc-7 && CXX=g++-7"
+        - EVAL="CC=gcc && CXX=g++"
         - CFLAGS="-Os"
         - LDFLAGS="-Wl,--no-undefined -lm"
         - QMAKEFLAGS="-config release"
+        - QT_NO_CPU_FEATURE=rdrnd
     - os: linux
+      dist: xenial
       addons:
         apt:
           sources:
-            - ubuntu-toolchain-r-test
-            - sourceline: 'ppa:beineri/opt-qt596-trusty'
+            - sourceline: 'ppa:beineri/opt-qt-5.12.1-xenial'
           packages:
-            - qt59base
+            - qt512base
       env:
         - QMAKESPEC=linux-clang
-        - EVAL="CC=clang-5.0 && CXX=clang++"
-        - PATH=$PATH:/usr/local/clang/bin
+        - EVAL="CC=clang && CXX=clang++"
         - CFLAGS="-Oz"
         - LDFLAGS="-Wl,--no-undefined -lm"
         - QMAKEFLAGS="-config release"
         - MAKEFLAGS=-s
         - TESTARGS=-silent
     - os: linux
+      dist: xenial
       env:
         - QMAKESPEC=linux-gcc-freestanding
         - EVAL="CXX=false"
         - CFLAGS="-ffreestanding -Os"
         - LDFLAGS="-Wl,--no-undefined -lm"
     - os: linux
+      dist: xenial
       env:
         - QMAKESPEC=linux-gcc-no-math
         - EVAL="CXX=false && touch src/math.h src/float.h"