Add a CMake debug include, with simple variables dump for development

cmake/CMakeDebugMacros.cmake

@@ -0,0 +1,42 @@
+# Macros/functions for debugging CMake
+# ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+#
+# Copyright (c) 2016, Larry Shaffer, <lshaffer (at) boundlessgeo (dot) com>>
+# Redistribution and use is allowed according to the terms of the BSD license.
+# For details see the accompanying COPYING-CMAKE-SCRIPTS file.
+
+
+# Dump current CMake variables to file
+#
+# Usage:
+# INCLUDE(CMakeDebugMacros)
+# DUMP_CMAKE_VARS()  or  DUMP_CMAKE_VARS("regex")
+#
+# regex: optional ARGV0 regular expression for filtering output variable names
+#
+# Outputs the result relative to the current CMake file being processed and
+# writes to a file with name "<file-basename>_cmake-vars.txt" to the current
+# build (binary) directory
+#
+function(DUMP_CMAKE_VARS)
+
+  get_filename_component(_basename ${CMAKE_CURRENT_LIST_FILE} NAME_WE)
+  set(_out "${CMAKE_CURRENT_BINARY_DIR}/${_basename}_cmake-vars.txt")
+
+  set(_cmake_vars "")
+  get_cmake_property(_varNames VARIABLES)
+  foreach(_varName ${_varNames})
+    if(ARGV0)
+      string(REGEX MATCH "${ARGV0}" _match "${_varName}")
+      if(_match)
+        set(_cmake_vars "${_cmake_vars}\n\n${_varName}=${${_varName}}")
+      endif()
+    else()
+      set(_cmake_vars "${_cmake_vars}\n\n${_varName}=${${_varName}}")
+    endif()
+  endforeach()
+
+  message(STATUS "Dumping current CMake variables to ...\n  ${_out}")
+  file(WRITE "${_out}" "${_cmake_vars}")
+
+endfunction(DUMP_CMAKE_VARS)