travis: enable -Werror in the script instead of using the matrix

.travis.yml

@@ -17,8 +17,8 @@ env:
   - secure: "YnhS+8n6B+uoyaYfaJ3Lei7cSJqHDPiKJCKFIF2c87YDfmCvAJke8QtE7IzjYDs7UFkTCM4ox+ph2bERUrxZbSCyEkHdjIZpKuMJfYWja/jgMqTMxdyOH9y8JLFbZsSXDIXDwqBlC6vVyl1fP90M35wuWcNTs6tctfVWVofEFbs="
   - GITTEST_INVASIVE_FS_SIZE=1
  matrix:
-  - OPTIONS="-DTHREADSAFE=ON -DENABLE_TRACE=ON -DCMAKE_BUILD_TYPE=Release -DENABLE_WERROR=ON"
-  - OPTIONS="-DTHREADSAFE=OFF -DBUILD_EXAMPLES=ON -DENABLE_WERROR=ON"
+  - OPTIONS="-DTHREADSAFE=ON -DENABLE_TRACE=ON -DCMAKE_BUILD_TYPE=Release"
+  - OPTIONS="-DTHREADSAFE=OFF -DBUILD_EXAMPLES=ON"
 
 dist: trusty
 sudo: false

script/cibuild.sh

@@ -23,5 +23,5 @@ fi
 mkdir _build
 cd _build
 # shellcheck disable=SC2086
-cmake .. -DBUILD_EXAMPLES=ON -DCMAKE_INSTALL_PREFIX=../_install $OPTIONS || exit $?
+cmake .. -DBUILD_EXAMPLES=ON -DENABLE_WERROR=ON -DCMAKE_INSTALL_PREFIX=../_install $OPTIONS || exit $?
 cmake --build . --target install || exit $?