Fix Sonarcloud sonar-project.properties (#120)

Fixes the emitted sonar.properties file so that header and test files
are picked up by Sonarcloud analysis.

According to the docs `sonar.tests` is ignored for C/C++ code, so
test paths should be treated the same as source paths.

Also switches `sonar.inclusions` with `sonar.sources` to fix the include
paths being filtered out.

Sonarcloud.cmake

@@ -199,13 +199,9 @@ function(generate_sonarcloud_project_properties sonarcloud_project_properties_pa
 
   set(sonarcloud_project_properties_content "sonar.sourceEncoding=UTF-8\n")
 
-  set(source_files ${source_source_files} ${source_include_directories})
+  set(source_files ${source_source_files} ${source_include_directories} ${test_source_files})
   list(JOIN source_files ",${_sonarcloud_newline}" sonar_sources)
-  string(APPEND sonarcloud_project_properties_content "sonar.inclusions=${_sonarcloud_newline}${sonar_sources}\n")
-
-  set(test_files ${test_source_files})
-  list(JOIN test_files ",${_sonarcloud_newline}" sonar_tests)
-  string(APPEND sonarcloud_project_properties_content "sonar.tests.inclusions=${_sonarcloud_newline}${sonar_tests}\n")
+  string(APPEND sonarcloud_project_properties_content "sonar.sources=${_sonarcloud_newline}${sonar_sources}\n")
 
   file(GENERATE
     OUTPUT "${sonarcloud_project_properties_path}"