Add support for fastcov

Since gcc-9, lcov is *very very* slow.
This allows the use of fastcov which runs approximately 100 times
faster (sic!)

CMakeLists.txt

@@ -335,6 +335,31 @@ if("${CMAKE_BUILD_TYPE}" STREQUAL "Coverage")
      message(FATAL_ERROR "Cannot find a proper gcov tool, cannot perform coverage.")
   endif()
 
+  find_program(FASTCOV fastcov fastcov.py)
+
+  if (FASTCOV AND (CMAKE_CXX_COMPILER_ID STREQUAL "GNU") AND (CMAKE_CXX_COMPILER_VERSION VERSION_GREATER "9"))
+
+    add_custom_target(coverage
+      ALL # in coverage mode we do coverage!
+
+      # Run tests
+      COMMAND ${CMAKE_CTEST_COMMAND} -j ${PROCESSOR_COUNT}
+
+      COMMAND ${FASTCOV} -q --gcov "${GCOV_BIN}"
+      --include "${PUGS_SOURCE_DIR}/src"
+      --exclude "${PUGS_SOURCE_DIR}/src/main.cpp"
+      --exclude "${PUGS_SOURCE_DIR}/src/utils/BacktraceManager.*"
+      --lcov -o coverage.info -n
+
+      COMMAND ${LCOV} --gcov "${GCOV_BIN}" --list coverage.info
+
+      DEPENDS unit_tests mpi_unit_tests
+      COMMENT "Running test coverage."
+      WORKING_DIRECTORY "${PUGS_BINARY_DIR}"
+      )
+
+  else()
+
     add_custom_target(coverage
       ALL # in coverage mode we do coverage!
       # Cleanup previously generated profiling data
@@ -354,7 +379,7 @@ if("${CMAKE_BUILD_TYPE}" STREQUAL "Coverage")
       # Remove unwanted stuff
       COMMAND ${LCOV} --gcov "${GCOV_BIN}" --remove coverage_extract.info  --output-file coverage.info
       '${PUGS_SOURCE_DIR}/src/main.cpp'
-                                              '${PUGS_SOURCE_DIR}/utils/BacktraceManager.*'
+      '${PUGS_SOURCE_DIR}/src/utils/BacktraceManager.*'
 
       COMMAND ${LCOV} --gcov "${GCOV_BIN}" --list coverage.info
 
@@ -362,6 +387,8 @@ if("${CMAKE_BUILD_TYPE}" STREQUAL "Coverage")
       COMMENT "Running test coverage."
       WORKING_DIRECTORY "${PUGS_BINARY_DIR}"
       )
+  endif()
+
 
   find_program(GENHTML genhtml)
   if(NOT GENHTML)