docs: generate translated .so manpage stubs from the English original

A .so alias stub is a redirect page with no prose; its body is just a
path to the page it aliases, identical in every language. asciidoctor
emits these stubs as a byproduct when it renders a translated primary
page whose NAME line lists several functions, deriving the path from the
translated NAME line. A stray space in the translation ("name , other"
instead of "name, other") then lands in the path, producing a broken
alias that aborts the htmldocs build via lang_switcher_postprocess.py.

Stop deriving the alias from translated text: once the translated
primaries are built, overwrite every translated .so stub with the
canonical English one. This fixes the roff page too (not just the HTML
symlink), and removes the only path by which a translation can break the
build. The stub list is discovered at recipe time because the
wildcard-based MAN_SRCS is empty on a clean build.

Author: grandixximo

docs/src/Submakefile

@@ -1325,6 +1325,7 @@ docclean:
 	-rm -f $(DOC_DIR)/.translateddocs-stamp
 	-rm -f $(DOC_DIR)/.gen_complist-stamp
 	-rm -f $(DOC_DIR)/.checkref-*-stamp
+	-rm -f $(DOC_DIR)/.manso-canonical-stamp
 	-rm -f $(OTHER_DOTFILES:.dot=.svg)
 
 
@@ -1425,6 +1426,27 @@ TRANSLATED_MAN_HTML_TARGETS := $(foreach L,$(LANGUAGES),$(MAN_HTML_TARGETS_$(cal
 TRANSLATED_GENERATED_MANPAGES := $(foreach L,$(LANGUAGES), \
     $(patsubst $(DOC_OUT_ADOC)/$(L)/man/%.adoc, $(DOC_MAN)/$(L)/%, \
         $(wildcard $(DOC_OUT_ADOC)/$(L)/man/man?/*.adoc)))
+
+# A .so alias stub is a language-invariant redirect (just a path).  asciidoctor
+# derives it from the translated NAME line, so a stray space in a translation
+# can break the alias and abort the build.  Overwrite every translated stub
+# with the canonical English one, after the translated primaries that emit them
+# are built.  Stubs are found at recipe time: wildcard MAN_SRCS is empty on a
+# clean build.
+$(DOC_DIR)/.manso-canonical-stamp: $(GENERATED_MANPAGES) $(TRANSLATED_GENERATED_MANPAGES)
+	$(Q)set -e; \
+	for S in $$(cd $(DOC_MAN) && grep -rl '^\.so ' man1 man3 man9 2>/dev/null); do \
+		for L in $(LANGUAGES); do \
+			mkdir -p "$(DOC_MAN)/$$L/$$(dirname "$$S")"; \
+			cp -f "$(DOC_MAN)/$$S" "$(DOC_MAN)/$$L/$$S"; \
+		done; \
+	done
+	@touch $@
+
+# Translated manpage HTML must see the canonical stubs, so order it after the
+# fixup (order-only: the stub troff is already a normal prerequisite).
+$(TRANSLATED_MAN_HTML_TARGETS): | $(DOC_DIR)/.manso-canonical-stamp
+
 docs: $(TRANSLATED_MAN_HTML_TARGETS)
 .SECONDARY: $(TRANSLATED_MAN_HTML_TARGETS) $(TRANSLATED_GENERATED_MANPAGES)
 endif