"--enable-doc-gen" configure flag will enable HTML document generation that requires mdbook.
We can't simply disable it because we need manpages.

Author: Zhu Zihao <all_but_last@163.com>

--- a/doc/manual/local.mk
+++ b/doc/manual/local.mk
@@ -138,11 +138,6 @@
 	$(trace-gen) $(dummy-env) NIX_PATH=nix/corepkgs=corepkgs $(bindir)/nix __dump-builtins > $@.tmp
 	@mv $@.tmp $@
 
-# Generate the HTML manual.
-.PHONY: manual-html
-manual-html: $(docdir)/manual/index.html
-install: $(docdir)/manual/index.html
-
 # Generate 'nix' manpages.
 install: $(mandir)/man1/nix3-manpages
 man: doc/manual/generated/man1/nix3-manpages
@@ -167,23 +162,4 @@
 	done
 	@touch $@
 
-$(docdir)/manual/index.html: $(MANUAL_SRCS) $(d)/book.toml $(d)/anchors.jq $(d)/custom.css $(d)/src/SUMMARY.md $(d)/src/command-ref/new-cli $(d)/src/contributing/experimental-feature-descriptions.md $(d)/src/command-ref/conf-file.md $(d)/src/language/builtins.md
-	$(trace-gen) \
-		tmp="$$(mktemp -d)"; \
-		cp -r doc/manual "$$tmp"; \
-		find "$$tmp" -name '*.md' | while read -r file; do \
-			$(call process-includes,$$file,$$file); \
-		done; \
-		find "$$tmp" -name '*.md' | while read -r file; do \
-			docroot="$$(realpath --relative-to="$$(dirname "$$file")" $$tmp/manual/src)"; \
-			sed -i "s,@docroot@,$$docroot,g" "$$file"; \
-		done; \
-		set -euo pipefail; \
-		RUST_LOG=warn mdbook build "$$tmp/manual" -d $(DESTDIR)$(docdir)/manual.tmp 2>&1 \
-			| { grep -Fv "because fragment resolution isn't implemented" || :; }; \
-		rm -rf "$$tmp/manual"
-	@rm -rf $(DESTDIR)$(docdir)/manual
-	@mv $(DESTDIR)$(docdir)/manual.tmp/html $(DESTDIR)$(docdir)/manual
-	@rm -rf $(DESTDIR)$(docdir)/manual.tmp
-
 endif
den' name='id' value='54edc96c4d85c55feb0f64fdc1919c7d26b6e13b'/><input type='hidden' name='showmsg' value='1'/><select name='qt'>
<option value='grep'>log msg</option>
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</td></tr></table>
<div class='path'>path: <a href='/guix/log/?id=54edc96c4d85c55feb0f64fdc1919c7d26b6e13b&amp;showmsg=1'>root</a>/<a href='/guix/log/gnu?id=54edc96c4d85c55feb0f64fdc1919c7d26b6e13b&amp;showmsg=1'>gnu</a>/<a href='/guix/log/gnu/services?id=54edc96c4d85c55feb0f64fdc1919c7d26b6e13b&amp;showmsg=1'>services</a>/<a href='/guix/log/gnu/services/vnc.scm?id=54edc96c4d85c55feb0f64fdc1919c7d26b6e13b&amp;showmsg=1'>vnc.scm</a></div><div class='content'><table class='list nowrap'><tr class='nohover'><th class='left'>Age</th><th class='left'>Commit message (<a href='/guix/log/gnu/services/vnc.scm?id=54edc96c4d85c55feb0f64fdc1919c7d26b6e13b'>Collapse</a>)</th><th class='left'>Author</th></tr>
<tr class='logheader'><td><span title='2023-05-21 01:04:39 +0200'>2023-05-21</span></td><td class='logsubject'><a href='/guix/commit/gnu/services/vnc.scm?id=896a51258aa71a483d8f6be29169098de5967baa'>services: Transient inetd services inherit requirements.</a></td><td>Ludovic Courtès</td></tr>
<tr class='nohover-highlight'><td/><td colspan='3' class='logmsg'>
That way, per-connection transient services such as 'sshd-123' inherit
dependencies of their "parent" ('sshd' in this example), which is more
consistent than not depending on anything.

* gnu/services/dict.scm (dicod-shepherd-service): Pass #:requirements to
'make-inetd-constructor'.
* gnu/services/messaging.scm (bitlbee-shepherd-service): Likewise.
* gnu/services/ssh.scm (openssh-shepherd-service): Likewise.
* gnu/services/vnc.scm (xvnc-shepherd-service): Likewise.


</td></tr>
<tr class='logheader'><td><span title='2023-04-02 23:35:15 -0400'>2023-04-02</span></td><td class='logsubject'><a href='/guix/commit/gnu/services/vnc.scm?id=1d0158ab9036cff7737cbfb1678f876ae67c4ac2'>services: xvnc: Do not create a regular HOME directory for xvnc user.</a></td><td>Maxim Cournoyer</td></tr>
<tr class='nohover-highlight'><td/><td colspan='3' class='logmsg'>
* gnu/services/vnc.scm (%xvnc-accounts)
[home-directory]: Define as /var/empty.
[shell]: Set to nologin, for good measures.


</td></tr>