[gcc r13-3537] Document 'distclean-stage[N]'

[Thomas Schwinge <tschwinge@gcc.gnu.org>]

https://gcc.gnu.org/g:0c112651f665be9948086f25f99d4e88c94716bd

commit r13-3537-g0c112651f665be9948086f25f99d4e88c94716bd
Author: Thomas Schwinge <thomas@codesourcery.com>
Date:   Wed Oct 26 13:07:27 2022 +0200

    Document 'distclean-stage[N]'
    
    Refer to 'Makefile.tpl':
    
        # Rules to wipe a stage and all the following ones, also used for cleanstrap
        [+ IF prev +]distclean-stage[+prev+]:: distclean-stage[+id+] [+ ENDIF prev +]
        .PHONY: distclean-stage[+id+]
        distclean-stage[+id+]::
            @: $(MAKE); $(stage)
            @test "`cat stage_last`" != stage[+id+] || rm -f stage_last
            rm -rf stage[+id+]-* [+
              IF compare-target +][+compare-target+] [+ ENDIF compare-target +]
    
            gcc/
            * doc/makefile.texi (Makefile Targets): Document
            'distclean-stage[N]'.

Diff:
---
 gcc/doc/makefile.texi | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/gcc/doc/makefile.texi b/gcc/doc/makefile.texi
index fe0bbcd2ed1..5186c1cd9d5 100644
--- a/gcc/doc/makefile.texi
+++ b/gcc/doc/makefile.texi
@@ -135,6 +135,16 @@ Compares the results of stages 2 and 3.  This ensures that the compiler
 is running properly, since it should produce the same object files
 regardless of how it itself was compiled.
 
+@item distclean-stage@var{N} (@var{N} = 1@dots{}4, profile, feedback)
+Wipe stage @var{N} and all the following ones.
+
+For example,
+@samp{make distclean-stage3} wipes stage 3 and all the following ones,
+so that another @command{make} then rebuilds them from scratch.
+This can be useful if you're doing changes where
+``bubbling'' the changes as described above is not sufficient,
+but a full @command{make restrap} isn't necessary either.
+
 @item profiledbootstrap
 Builds a compiler with profiling feedback information.  In this case,
 the second and third stages are named @samp{profile} and @samp{feedback},