travis: add CC_VERSION=8

clang-8 is experimental so allows its failure on os: linux

.travis.yml

@@ -31,11 +31,15 @@ env:
     - CC_VERSION=7 TYPE=RelWithDebInfo MYSQL_TEST_SUITES=binlog,binlog_encryption,encryption
     - CC_VERSION=7 TYPE=RelWithDebInfo MYSQL_TEST_SUITES=rocksdb
     - CC_VERSION=7 TYPE=RelWithDebInfo MYSQL_TEST_SUITES=csv,federated,funcs_1,funcs_2,gcol,handler,heap,json,maria,perfschema,plugins,multi_source,roles
+    - CC_VERSION=8 TYPE=RelWithDebInfo MYSQL_TEST_SUITES=main
 
 matrix:
   exclude:
     - os: osx
       compiler: gcc
+    - os: osx
+      compiler: clang
+      env: CC_VERSION=8 TYPE=RelWithDebInfo MYSQL_TEST_SUITES=main
   include:
     - os: linux
       compiler: gcc
@@ -106,22 +110,30 @@ matrix:
     - os: osx
       compiler: clang
       env: CC_VERSION=7 TYPE=RelWithDebInfo MYSQL_TEST_SUITES=csv,federated,funcs_1,funcs_2,gcol,handler,heap,json,maria,perfschema,plugins,multi_source,roles
+    - os: linux
+      compiler: clang
+      env: CC_VERSION=8 TYPE=RelWithDebInfo MYSQL_TEST_SUITES=main
 
 addons:
   apt:
     sources:
       - ubuntu-toolchain-r-test
       - llvm-toolchain-trusty-6.0
       - llvm-toolchain-trusty-7
+      - llvm-toolchain-trusty
     packages: # make sure these include all compilers and all build dependencies (see list above)
       - gcc-6
       - g++-6
       - gcc-7
       - g++-7
+      - gcc-8
+      - g++-8
       - clang-6.0
       - llvm-6.0-dev
       - clang-7
       - llvm-7-dev
+      - clang-8
+      - llvm-8-dev
       - bison
       - chrpath
       - cmake