XL: Place Fortran modules with -qmoddir= flag (#12246)

Suggested-by: Luis Kornblueh <luis.kornblueh@zmaw.de>

Modules/Compiler/XL-Fortran.cmake

@@ -1,6 +1,8 @@
 include(Compiler/XL)
 __compiler_xl(Fortran)
 
+SET(CMAKE_Fortran_MODDIR_FLAG "-qmoddir=")
+
 SET(CMAKE_Fortran_DEFINE_FLAG "-WF,-D")
 
 # -qthreaded     = Ensures that all optimizations will be thread-safe