COMP: Limit load for macOS 13 Intel builds

The load gets too high and the build is extremely slow.

Author: thewtex

CMakeLists.txt

@@ -29,6 +29,12 @@ if(ITKPythonPackage_USE_TBB)
     )
 endif()
 
+if(${CMAKE_GENERATOR} STREQUAL "Ninja")
+  include(ProcessorCount)
+  ProcessorCount(n_processors)
+  set(ep_build_command BUILD_COMMAND ${CMAKE_COMMAND} --build <BUILD_DIR> -- -j${n_processors} -l${n_processors})
+endif()
+
 if(ITKPythonPackage_SUPERBUILD)
 
   #-----------------------------------------------------------------------------
@@ -117,6 +123,7 @@ if(ITKPythonPackage_SUPERBUILD)
     ExternalProject_add(oneTBB
       URL https://github.com/oneapi-src/oneTBB/archive/refs/tags/v2021.9.0.tar.gz
       URL_HASH SHA256=1ce48f34dada7837f510735ff1172f6e2c261b09460e3bf773b49791d247d24e
+      ${ep_build_command}
       CMAKE_ARGS
         -DTBB_TEST:BOOL=OFF
         -DCMAKE_BUILD_TYPE:STRING=Release
@@ -265,6 +272,7 @@ if(ITKPythonPackage_SUPERBUILD)
 
     ExternalProject_add(ITK
       DOWNLOAD_COMMAND ""
+      ${ep_build_command}
       SOURCE_DIR ${ITK_SOURCE_DIR}
       BINARY_DIR ${ITK_BINARY_DIR}
       PREFIX "ITKp"

scripts/macpython-build-wheels.sh

@@ -63,6 +63,7 @@ fi
 
 # Build standalone project and populate archive cache
 tbb_dir=$PWD/oneTBB-prefix/lib/cmake/TBB
+n_processors=$(sysctl -n hw.ncpu)
 # So delocate can find the libs
 export DYLD_LIBRARY_PATH=${DYLD_LIBRARY_PATH}:$PWD/oneTBB-prefix/lib
 mkdir -p ITK-source
@@ -75,7 +76,7 @@ pushd ITK-source > /dev/null 2>&1
     -DCMAKE_OSX_DEPLOYMENT_TARGET:STRING=${osx_target} \
     -DCMAKE_OSX_ARCHITECTURES:STRING=${osx_arch} \
       ${SCRIPT_DIR}/../
-  ${NINJA_EXECUTABLE}
+  ${NINJA_EXECUTABLE} -j$n_processors -l$n_processors
 popd > /dev/null 2>&1
 
 SINGLE_WHEEL=0
@@ -170,7 +171,7 @@ for VENV in "${VENVS[@]}"; do
           ${CMAKE_OPTIONS} \
           -G Ninja \
           ${source_path} \
-        && ninja\
+        && ninja -j$n_processors -l$n_processors \
         || exit 1
       )