Help: Document CMAKE_FIND_DEBUG_MODE

Help/manual/cmake-variables.7.rst

@@ -53,6 +53,7 @@ Variables that Provide Information
    /variable/CMAKE_EXECUTABLE_SUFFIX
    /variable/CMAKE_EXTRA_GENERATOR
    /variable/CMAKE_EXTRA_SHARED_LIBRARY_SUFFIXES
+   /variable/CMAKE_FIND_DEBUG_MODE
    /variable/CMAKE_FIND_PACKAGE_NAME
    /variable/CMAKE_FIND_PACKAGE_SORT_DIRECTION
    /variable/CMAKE_FIND_PACKAGE_SORT_ORDER

Help/variable/CMAKE_FIND_DEBUG_MODE.rst

@@ -0,0 +1,22 @@
+CMAKE_FIND_DEBUG_MODE
+---------------------
+
+Print extra find call information for the following commands to standard
+error:
+* :command:`find_program`
+* :command:`find_library`
+* :command:`find_file`
+* :command:`find_path`
+* :command:`find_package`
+
+Output is designed for human consumption and not for parsing.
+Enabling this variable is equivalent to using :manual:`cmake <cmake(1)>` ``--debug-find``
+with the added ability to enable debugging for a subset of find calls.
+
+.. code-block:: cmake
+
+  set(CMAKE_FIND_DEBUG_MODE TRUE)
+  find_program(...)
+  set(CMAKE_FIND_DEBUG_MODE FALSE)
+
+Default is unset.