Use add_compile_options to apply compiler flags

Since compiler flags are the same across all targets, this change
applies the flags globally to all targets in the current directory and
below.

CMakeLists.txt

@@ -19,8 +19,7 @@ set(CABLE_Intel_Fortran_FLAGS -fp-model precise)
 set(CABLE_Intel_Fortran_FLAGS_DEBUG -O0 -g -traceback -fpe0)
 set(CABLE_Intel_Fortran_FLAGS_RELEASE -O2)
 if(CMAKE_Fortran_COMPILER_ID MATCHES "Intel")
-    set(
-        CABLE_Fortran_FLAGS
+    add_compile_options(
         ${CABLE_Intel_Fortran_FLAGS}
         "$<$<CONFIG:Release>:${CABLE_Intel_Fortran_FLAGS_RELEASE}>"
         "$<$<CONFIG:Debug>:${CABLE_Intel_Fortran_FLAGS_DEBUG}>"
@@ -31,8 +30,7 @@ set(CABLE_GNU_Fortran_FLAGS -cpp -ffree-form -ffixed-line-length-132)
 set(CABLE_GNU_Fortran_FLAGS_DEBUG -O -g -pedantic-errors -Wall -W -Wno-maybe-uninitialized -fbacktrace -ffpe-trap=zero,overflow,underflow -finit-real=nan)
 set(CABLE_GNU_Fortran_FLAGS_RELEASE -O3 -Wno-aggressive-loop-optimizations)
 if(CMAKE_Fortran_COMPILER_ID MATCHES "GNU")
-    set(
-        CABLE_Fortran_FLAGS
+    add_compile_options(
         ${CABLE_GNU_Fortran_FLAGS}
         "$<$<CONFIG:Release>:${CABLE_GNU_Fortran_FLAGS_RELEASE}>"
         "$<$<CONFIG:Debug>:${CABLE_GNU_Fortran_FLAGS_DEBUG}>"
@@ -151,15 +149,13 @@ add_library(
     src/util/cable_runtime_opts_mod.F90
     src/util/masks_cbl.F90
 )
-target_compile_options(cable_common_objlib PRIVATE ${CABLE_Fortran_FLAGS})
 target_link_libraries(cable_common_objlib PRIVATE PkgConfig::NETCDF)
 
 add_executable(
     cable
     src/offline/cable_driver.F90
     "$<TARGET_OBJECTS:cable_common_objlib>"
 )
-target_compile_options(cable PRIVATE ${CABLE_Fortran_FLAGS})
 target_link_libraries(cable PRIVATE PkgConfig::NETCDF)
 install(TARGETS cable RUNTIME)
 
@@ -173,7 +169,6 @@ if(CABLE_MPI)
         src/science/pop/pop_mpi.F90
         "$<TARGET_OBJECTS:cable_common_objlib>"
     )
-    target_compile_options(cable-mpi PRIVATE ${CABLE_Fortran_FLAGS})
     target_link_libraries(cable-mpi PRIVATE PkgConfig::NETCDF MPI::MPI_Fortran)
     install(TARGETS cable-mpi RUNTIME)
 endif()