v: use dash instead of lowerdash for -print-v-files (#9111)

cmd/tools/vcomplete.v

@@ -129,7 +129,7 @@ const (
 		'-W',
 		'-keepc',
 		'-w',
-		'-print_v_files',
+		'-print-v-files',
 		'-error-limit',
 		'-os',
 		'-printfn',

cmd/v/help/build.txt

@@ -103,13 +103,13 @@ NB: the build flags are shared with the run command too:
    -v
       Enable verbosity in the V compiler while compiling
 
-   -print_v_files
+   -print-v-files
       Just print the list of all parsed .v files, then stop processing further.
       This is useful for running external processing tools:
-        ./v -print_v_files cmd/v | etags -L -
+        ./v -print-v-files cmd/v | etags -L -
       ... will generate a TAGS file, that emacs can then use to jump
       to the definition of functions used by v itself. For vim:
-        ./v -print_v_files cmd/v | ctags -L -
+        ./v -print-v-files cmd/v | ctags -L -
       ... will generate a simillar tags file, that vi compatible editors can use.
       NB: an useful, although not entirely accurate regexp based Universal Ctags options file
       for V is located in `.ctags.d/v.ctags` . If you use https://ctags.io/ , it will be used

vlib/v/pref/pref.v

@@ -329,7 +329,7 @@ pub fn parse_args(known_external_commands []string, args []string) (&Preferences
 			'-w' {
 				res.skip_warnings = true
 			}
-			'-print_v_files' {
+			'-print-v-files' {
 				res.print_v_files = true
 			}
 			'-error-limit' {