Add clang-tidy, create Linux build script

clang-tidy is currently set up with errors for all checks that do not
warn. This is to prevent regressing the repo.

Gradually these warnings should be removed in order to prevent further
regresssions in warnings that do not have many occurences.

.travis.yml

@@ -12,10 +12,17 @@ matrix:
         - g++-7
     env:
     - QMAKE_SPEC=linux-g++
+    compiler: gcc
 
   - os: linux
     env:
     - QMAKE_SPEC=linux-clang
+    compiler: clang
+
+  - os: linux
+    env:
+    - USE_TIDY=TRUE
+    compiler: clang
 
 before_install:
   - python ./build_scripts/run-clang-format.py ./src -r --color always  
@@ -24,9 +31,7 @@ install:
   - sudo add-apt-repository ppa:kubuntu-ppa/backports -y
   - sudo apt-get update -qq
   - sudo apt-get install build-essential qtbase5-dev qttools5-dev qtdeclarative5-dev qtmultimedia5-dev qt5-default qttools5-dev-tools
+  - sudo apt-get install bear clang-tidy
 
 script:
-  - mkdir build && cd build
-  - qmake --version
-  - qmake .. -spec $QMAKE_SPEC
-  - make
+  - ./build_scripts/linux/build_linux.sh