Add first version of whitespace utility

cmake/Modules/CodingStandard.cmake

@@ -0,0 +1,21 @@
+if(CMAKE_VERSION VERSION_LESS 3.12)
+    find_package(PythonInterp) # Deprecated since version 3.12
+    if(PYTHONINTERP_FOUND)
+        set(Python_EXECUTABLE ${PYTHON_EXECUTABLE})
+    endif()
+else()
+    find_package(Python COMPONENTS Interpreter)
+endif()
+
+if (Python_EXECUTABLE)
+    add_custom_target(
+      check-whitespace
+      ${Python_EXECUTABLE} ${LAMMPS_TOOLS_DIR}/coding_standard/whitespace.py .
+      WORKING_DIRECTORY  ${LAMMPS_DIR}
+      COMMENT "Check for whitespace errors")
+    add_custom_target(
+      fix-whitespace
+      ${Python_EXECUTABLE} ${LAMMPS_TOOLS_DIR}/coding_standard/whitespace.py -f .
+      WORKING_DIRECTORY  ${LAMMPS_DIR}
+      COMMENT "Fix whitespace errors")
+endif()