src: mention that node options are space-separated

The documentation does not mention that the value of NODE_OPTIONS is a
space-separated list.

PR-URL: #14709
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Khaidi Chu <i@2333.moe>
Reviewed-By: Vse Mozhet Byt <vsemozhetbyt@gmail.com>
Reviewed-By: Gibson Fahnestock <gibfahn@gmail.com>

doc/api/cli.md

@@ -440,10 +440,10 @@ When set to `1`, process warnings are silenced.
 added: v8.0.0
 -->
 
-`options...` are interpreted as if they had been specified on the command line
-before the actual command line (so they can be overridden).  Node will exit with
-an error if an option that is not allowed in the environment is used, such as
-`-p` or a script file.
+A space-separated list of command line options. `options...` are interpreted as
+if they had been specified on the command line before the actual command line
+(so they can be overridden).  Node will exit with an error if an option that is
+not allowed in the environment is used, such as `-p` or a script file.
 
 Node options that are allowed are:
 - `--enable-fips`

doc/node.1

@@ -282,10 +282,10 @@ When set to \fI1\fR, process warnings are silenced.
 
 .TP
 .BR NODE_OPTIONS =\fIoptions...\fR
-\fBoptions...\fR are interpreted as if they had been specified on the command
-line before the actual command line (so they can be overridden).  Node will exit
-with an error if an option that is not allowed in the environment is used, such
-as \fB-p\fR or a script file.
+A space-separated list of command line options. \fBoptions...\fR are interpreted
+as if they had been specified on the command line before the actual command line
+(so they can be overridden).  Node will exit with an error if an option that is
+not allowed in the environment is used, such as \fB-p\fR or a script file.
 
 .TP
 .BR NODE_PATH =\fIpath\fR[:\fI...\fR]

src/node.cc

@@ -3722,6 +3722,7 @@ static void PrintHelp() {
          "NODE_NO_WARNINGS             set to 1 to silence process warnings\n"
 #if !defined(NODE_WITHOUT_NODE_OPTIONS)
          "NODE_OPTIONS                 set CLI options in the environment\n"
+         "                             via a space-separated list\n"
 #endif
 #ifdef _WIN32
          "NODE_PATH                    ';'-separated list of directories\n"