Make sure find_package(NCrystal) also works with pip installed NCrystal

CMakeLists.txt

@@ -110,7 +110,15 @@ endmacro()
 #===============================================================================
 
 if(OPENMC_USE_NCRYSTAL)
-  find_package(NCrystal REQUIRED)
+  if( NOT DEFINED "NCrystal_DIR" )
+    #Invocation of "ncrystal-config --show cmakedir" is needed to find NCrystal
+    #even if it is installaed from Python wheels:
+    execute_process(
+      COMMAND "ncrystal-config" "--show" "cmakedir"
+      OUTPUT_VARIABLE "NCrystal_DIR" OUTPUT_STRIP_TRAILING_WHITESPACE
+    )
+  endif()
+  find_package(NCrystal 3.8.0 REQUIRED)
   message(STATUS "Found NCrystal: ${NCrystal_DIR} (version ${NCrystal_VERSION})")
 endif()
 

docs/source/usersguide/install.rst

@@ -287,9 +287,8 @@ Prerequisites
       Adding this option allows the creation of materials from NCrystal, which
       replaces the scattering kernel treatment of ACE files with a modular,
       on-the-fly approach. To use it `install
-      <https://github.com/mctools/ncrystal/wiki/Get-NCrystal>`_ and `initialize
-      <https://github.com/mctools/ncrystal/wiki/Using-NCrystal#setting-up>`_
-      NCrystal and turn on the option in the CMake configuration step::
+      <https://github.com/mctools/ncrystal/wiki/Get-NCrystal>`_ NCrystal and
+      turn on the option in the CMake configuration step::
 
           cmake -DOPENMC_USE_NCRYSTAL=on ..