Fix installation location for libraries (ECP-WarpX#2583)

During configuration the installation location for libraries is given by
dumping the cmake variable `CMAKE_INSTALL_LIBDIR`.
This commit adjusts the installation of WarpX libraries (WarpX_LIB=ON)
to respect this setting.

Co-authored-by: Rolf Pfeffertal <tropf@users.noreply.github.com>

CMakeLists.txt

@@ -345,7 +345,7 @@ if(WarpX_LIB)
     endif()
     install(CODE "file(CREATE_LINK
         $<TARGET_FILE_NAME:shared>
-        ${CMAKE_INSTALL_PREFIX}/${CMAKE_INSTALL_LIBDIR}/libwarpx.${lib_suffix}.${mod_ext}
+        ${CMAKE_INSTALL_LIBDIR}/libwarpx.${lib_suffix}.${mod_ext}
         COPY_ON_ERROR SYMBOLIC)")
 endif()