Remove extra GCC arquements.

"--coverage" is synonym to "-fprofile-arcs -ftest-coverage"
https://gcc.gnu.org/onlinedocs/gcc/Instrumentation-Options.html

This was causing extra compilation warnings on CLANG.

Author: Seppo Takalo

UNITTESTS/CMakeLists.txt

@@ -76,7 +76,7 @@ if (COVERAGE)
   endif()
 
   # Append coverage compiler flags
-  set(COVERAGE_COMPILER_FLAGS "-g -O0 --coverage -fprofile-arcs -ftest-coverage")
+  set(COVERAGE_COMPILER_FLAGS "-g -O0 --coverage")
   set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} ${COVERAGE_COMPILER_FLAGS}")
   set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} ${COVERAGE_COMPILER_FLAGS}")