Fix CMake IPO Control

`pybind11::lto` is only defined if `CMAKE_INTERPROCEDURAL_OPTIMIZATION`
is not set in `pybind11Common.cmake`. Package managers like Spack
use the latter.

CMakeLists.txt

@@ -68,9 +68,13 @@ pyamrex_set_default_install_dirs()
 
 # Options and Variants ########################################################
 #
+set(_pyAMReX_IPO_DEFAULT ON)
+if(DEFINED CMAKE_INTERPROCEDURAL_OPTIMIZATION)
+    set(_pyAMReX_IPO_DEFAULT ${CMAKE_INTERPROCEDURAL_OPTIMIZATION})
+endif()
 option(pyAMReX_IPO
     "Compile with interprocedural optimization (IPO) / link-time optimization (LTO)"
-    ON
+    ${_pyAMReX_IPO_DEFAULT}
 )
 option(pyAMReX_INSTALL
     "Enable install targets for pyAMReX"
@@ -134,7 +138,7 @@ foreach(D IN LISTS AMReX_SPACEDIM)
     # link dependencies
     target_link_libraries(pyAMReX_${D}d PUBLIC AMReX::amrex_${D}d)
     target_link_libraries(pyAMReX_${D}d PRIVATE pybind11::module pybind11::windows_extras)
-    if(pyAMReX_IPO)
+    if(pyAMReX_IPO AND NOT DEFINED CMAKE_INTERPROCEDURAL_OPTIMIZATION)
         target_link_libraries(pyAMReX_${D}d PRIVATE pybind11::lto)
     endif()