Thanks; that confirmed my suspicion that it wasn’t linking to gcov in the tests. The current workaround is placing:
set(CMAKE_REQUIRED_LIBRARIES gcov)
right before the check_fortran_compiler_flag() calls for --coverage and -fprofile-arcs
then call unset(CMAKE_REQUIRED_LIBRARIES).
This seems like good variable hygiene; my project typically uses target_link_libraries() and I otherwise don’t use CMAKE_REQUIRED_LIBRARIES. Is this liable to break anything else?
FWIW, diggging down to Internal/CheckSourceCompiles.cmake let me see what was going on. Setting CMAKE_REQUIRED_LIBRARIES seemed like the least worst option.