LATTE.cmake: fix build with ninja

cmake/Modules/Packages/LATTE.cmake

@@ -8,9 +8,6 @@ if(PKG_LATTE)
   endif()
   option(DOWNLOAD_LATTE "Download the LATTE library instead of using an already installed one" ${DOWNLOAD_LATTE_DEFAULT})
   if(DOWNLOAD_LATTE)
-    if(CMAKE_GENERATOR STREQUAL "Ninja")
-      message(FATAL_ERROR "Cannot build downloaded LATTE library with Ninja build tool")
-    endif()
     message(STATUS "LATTE download requested - we will build our own")
     include(ExternalProject)
     ExternalProject_Add(latte_build
@@ -21,6 +18,7 @@ if(PKG_LATTE)
       -DBLAS_LIBRARIES=${BLAS_LIBRARIES} -DLAPACK_LIBRARIES=${LAPACK_LIBRARIES}
       -DCMAKE_Fortran_COMPILER=${CMAKE_Fortran_COMPILER} -DCMAKE_Fortran_FLAGS=${CMAKE_Fortran_FLAGS}
       -DCMAKE_Fortran_FLAGS_${BTYPE}=${CMAKE_Fortran_FLAGS_${BTYPE}} -DCMAKE_BUILD_TYPE=${CMAKE_BUILD_TYPE}
+      BUILD_BYPRODUCTS <INSTALL_DIR>/${CMAKE_INSTALL_LIBDIR}/liblatte.a
     )
     ExternalProject_get_property(latte_build INSTALL_DIR)
     set(LATTE_LIBRARIES ${INSTALL_DIR}/${CMAKE_INSTALL_LIBDIR}/liblatte.a)