runtests.sh: refactoring and cleanups (#4029)

* runtests.sh: avoid redundant `pkg-config` checks and simplified the check

* runtests.sh: write a message when something is completely missing

* runtests.sh: derive paths from script location

* runtests.sh: improved readability by using individual functions for each file

* runtests.sh: added helper function `get_pkg_config_cflags()` to clean up cflag lookup from `pkg-config`

* runtests.sh: simplified `xmlstarlet` calls

Author: firewave

test/CMakeLists.txt

@@ -43,8 +43,7 @@ if (BUILD_TESTS)
         # TODO: get rid of the copy
         add_custom_target(checkcfg ${CMAKE_COMMAND} -E copy $<TARGET_FILE:cppcheck> ${CMAKE_SOURCE_DIR}
                 COMMAND ${CMAKE_CURRENT_SOURCE_DIR}/cfg/runtests.sh
-                DEPENDS cppcheck validateCFG
-                WORKING_DIRECTORY ${CMAKE_CURRENT_SOURCE_DIR}/cfg)
+                DEPENDS cppcheck validateCFG)
     endif()
 
     if (REGISTER_TESTS)