Help: Improve formatting of command documentation

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Help/command/execute_process.rst

@@ -26,7 +26,7 @@ A single standard error pipe is used for all processes.
 
 Options:
 
-COMMAND
+``COMMAND``
  A child process command line.
 
  CMake executes the child process using operating system APIs directly.
@@ -36,31 +36,31 @@ COMMAND
  (Use the ``INPUT_*``, ``OUTPUT_*``, and ``ERROR_*`` options to
  redirect stdin, stdout, and stderr.)
 
-WORKING_DIRECTORY
+``WORKING_DIRECTORY``
  The named directory will be set as the current working directory of
  the child processes.
 
-TIMEOUT
+``TIMEOUT``
  The child processes will be terminated if they do not finish in the
  specified number of seconds (fractions are allowed).
 
-RESULT_VARIABLE
+``RESULT_VARIABLE``
  The variable will be set to contain the result of running the processes.
  This will be an integer return code from the last child or a string
  describing an error condition.
 
-OUTPUT_VARIABLE, ERROR_VARIABLE
+``OUTPUT_VARIABLE``, ``ERROR_VARIABLE``
  The variable named will be set with the contents of the standard output
  and standard error pipes, respectively.  If the same variable is named
  for both pipes their output will be merged in the order produced.
 
-INPUT_FILE, OUTPUT_FILE, ERROR_FILE
+``INPUT_FILE, OUTPUT_FILE``, ``ERROR_FILE``
  The file named will be attached to the standard input of the first
  process, standard output of the last process, or standard error of
  all processes, respectively.  If the same file is named for both
  output and error then it will be used for both.
 
-OUTPUT_QUIET, ERROR_QUIET
+``OUTPUT_QUIET``, ``ERROR_QUIET``
  The standard output or standard error results will be quietly ignored.
 
 If more than one ``OUTPUT_*`` or ``ERROR_*`` option is given for the