[Patch] Fix AMReX::FFTW Once

Apply AMReX-Codes/amrex#4293
to fix conda-forge/impactx-feedstock#42

recipe/4293.patch

@@ -0,0 +1,43 @@
+From c6ee9704d892c18a21877920c43f07b542a03894 Mon Sep 17 00:00:00 2001
+From: Axel Huebl <axel.huebl@plasma.ninja>
+Date: Sat, 11 Jan 2025 17:23:29 -0800
+Subject: [PATCH] Fix `AMReX::FFTW` Once
+
+In situations like superbuilds or other downstream usage,
+the `AMReX::FFTW` should only be created once.
+---
+ Tools/CMake/FindAMReXFFTW.cmake | 14 ++++++++------
+ 1 file changed, 8 insertions(+), 6 deletions(-)
+
+diff --git a/Tools/CMake/FindAMReXFFTW.cmake b/Tools/CMake/FindAMReXFFTW.cmake
+index 64ce7183f3..1306ae77b8 100644
+--- a/Tools/CMake/FindAMReXFFTW.cmake
++++ b/Tools/CMake/FindAMReXFFTW.cmake
+@@ -102,9 +102,6 @@ if(NOT AMReX_FFTW_SEARCH IN_LIST AMReX_FFTW_SEARCH_VALUES)
+ endif()
+ mark_as_advanced(AMReX_FFTW_SEARCH)
+
+-# Create imported target
+-add_library(AMReX::FFTW INTERFACE IMPORTED GLOBAL)
+-
+ function(fftw_find_precision HFFTWp)
+     if(AMReX_FFTW_SEARCH STREQUAL CMAKE)
+         find_package(FFTW3${HFFTWp} CONFIG REQUIRED)
+@@ -138,9 +135,14 @@ function(fftw_find_precision HFFTWp)
+     endif()
+ endfunction()
+
+-# floating point precision suffixes: we request float and double precision
+-fftw_find_precision("")
+-fftw_find_precision("f")
++if(NOT TARGET AMReX::FFTW)
++    # Create imported target
++    add_library(AMReX::FFTW INTERFACE IMPORTED GLOBAL)
++
++    # floating point precision suffixes: we request float and double precision
++    fftw_find_precision("")
++    fftw_find_precision("f")
++endif()
+
+ # Vars for CMake config
+ include(FindPackageHandleStandardArgs)

recipe/meta.yaml

@@ -1,6 +1,6 @@
 {% set name = "amrex" %}
 {% set version = "25.01" %}
-{% set build = 0 %}
+{% set build = 1 %}
 
 # ensure mpi is defined (needed for conda-smithy recipe-lint)
 {% set mpi = mpi or 'nompi' %}
@@ -17,6 +17,10 @@ package:
 source:
   url: https://github.com/AMReX-Codes/amrex/archive/refs/tags/{{ version }}.tar.gz
   sha256: e774ae6813b8a5dcbebdff1e7e052ac35059096f2542d61ef9bd161fd6fa6b1e
+  patches:
+    # Fix AMReX::FFTW Once
+    # https://github.com/AMReX-Codes/amrex/pull/4293
+    - 4293.patch
 
 build:
   number: {{ build }}