Update system.cmake

cmake/system.cmake

@@ -616,9 +616,11 @@ if (${CMAKE_SYSTEM_NAME} STREQUAL "Windows")
   endforeach ()
 endif ()
 
+if (CMAKE_Fortran_COMPILER)
 if (${F_COMPILER} STREQUAL "NAG" OR ${F_COMPILER} STREQUAL "CRAY" OR CMAKE_Fortran_COMPILER_ID MATCHES "LLVMFlang.*")
   set(FILTER_FLAGS "-msse3;-mssse3;-msse4.1;-mavx;-mavx2,-mskylake-avx512")
   if (CMAKE_Fortran_COMPILER_ID MATCHES "LLVMFlang.*")
+message(STATUS "removing fortran flags")
     set(FILTER_FLAGS "${FILTER_FLAGS};-m32;-m64")
   endif ()
   foreach (FILTER_FLAG ${FILTER_FLAGS})
@@ -626,6 +628,7 @@ if (${F_COMPILER} STREQUAL "NAG" OR ${F_COMPILER} STREQUAL "CRAY" OR CMAKE_Fortr
     string(REPLACE ${FILTER_FLAG} "" LAPACK_FPFLAGS ${LAPACK_FPFLAGS})
   endforeach ()
 endif ()
+endif ()
 
 if ("${F_COMPILER}" STREQUAL "GFORTRAN")
   # lapack-netlib is rife with uninitialized warnings -hpa