added script to enable coverage report

cmake/enable_code_coverage_report.cmake

+#######################################################################################################################
+# enable_code_coverage_report.cmake
+#
+# Enable possibility to generate a code coverage report when compiling in 'Debug' mode.
+# Configure with the option -DCMAKE_BUILD_TYPE=Debug.
+# It require working tests which can be called with 'make test'. The coverage is created
+# over these tests.
+#
+# You need lcov installed to use the 'make coverage' command.
+#
+# This script appends to the variable CMAKE_CXX_FLAGS_DEBUG,
+# and adds the target 'coverage', only available in 'Debug' mode.
+#
+#######################################################################################################################
+
+#######################################################################################################################
+#
+# IMPORTANT NOTE:
+#
+# DO NOT MODIFY THIS FILE inside a project. Instead update the project-template repository and pull the change from
+# there. Make sure to keep the file generic, since it will be used by other projects, too.
+#
+# If you have modified this file inside a project despite this warning, make sure to cherry-pick all your changes
+# into the project-template repository immediately.
+#
+#######################################################################################################################
+
+set(CMAKE_CXX_FLAGS_DEBUG "${CMAKE_CXX_FLAGS_DEBUG} -O0 --coverage")
+
+#The make coverage command is only available in debug mode
+IF(CMAKE_BUILD_TYPE STREQUAL "Debug")
+  configure_file(cmake/make_coverage.sh.in
+    ${PROJECT_BINARY_DIR}/make_coverage.sh @ONLY)
+  add_custom_target(coverage
+    ./make_coverage.sh
+    WORKING_DIRECTORY ${CMAKE_CURRENT_BINARY_DIR}
+    COMMENT "Generating test coverage documentation" VERBATIM
+    )
+ENDIF(CMAKE_BUILD_TYPE STREQUAL "Debug")
+