configure: Don't make shell completions without perl

The code that attempted to skip building the shell completions didn't
work properly and tried to build them even if perl wasn't available.
This step, as well as the install step, is now properly skipped without
perl.

Follow-up to 89733e2

Closes #13022

scripts/Makefile.am

@@ -40,28 +40,32 @@ $(ZSH_COMPLETION_FUNCTION_FILENAME): completion.pl
 if CROSSCOMPILING
 	@echo "NOTICE: we can't generate zsh completion when cross-compiling!"
 else # if not cross-compiling:
-	@if ! test -x "$(PERL)"; then echo "No perl: can't install completion script"; exit 0; fi
-	$(PERL) $(srcdir)/completion.pl --curl $(top_builddir)/src/curl$(EXEEXT) --shell zsh > $@
+	if test -z "$(PERL)"; then echo "No perl: can't install completion script"; else \
+	$(PERL) $(srcdir)/completion.pl --curl $(top_builddir)/src/curl$(EXEEXT) --shell zsh > $@ ; fi
 endif
 
 $(FISH_COMPLETION_FUNCTION_FILENAME): completion.pl
 if CROSSCOMPILING
 	@echo "NOTICE: we can't generate fish completion when cross-compiling!"
 else # if not cross-compiling:
-	@if ! test -x "$(PERL)"; then echo "No perl: can't install completion scriptl"; exit 0; fi
-	$(PERL) $(srcdir)/completion.pl --curl $(top_builddir)/src/curl$(EXEEXT) --shell fish > $@
+	if test -z "$(PERL)"; then echo "No perl: can't install completion script"; else \
+	$(PERL) $(srcdir)/completion.pl --curl $(top_builddir)/src/curl$(EXEEXT) --shell fish > $@ ; fi
 endif
 
 install-data-local:
 if CROSSCOMPILING
 	@echo "NOTICE: we can't install completion scripts when cross-compiling!"
 else # if not cross-compiling:
 if USE_ZSH_COMPLETION
-	$(MKDIR_P) $(DESTDIR)$(ZSH_FUNCTIONS_DIR)
-	$(INSTALL_DATA) $(ZSH_COMPLETION_FUNCTION_FILENAME) $(DESTDIR)$(ZSH_FUNCTIONS_DIR)/$(ZSH_COMPLETION_FUNCTION_FILENAME)
+	if test -n "$(PERL)"; then \
+	  $(MKDIR_P) $(DESTDIR)$(ZSH_FUNCTIONS_DIR); \
+	  $(INSTALL_DATA) $(ZSH_COMPLETION_FUNCTION_FILENAME) $(DESTDIR)$(ZSH_FUNCTIONS_DIR)/$(ZSH_COMPLETION_FUNCTION_FILENAME) ; \
+  fi
 endif
 if USE_FISH_COMPLETION
-	$(MKDIR_P) $(DESTDIR)$(FISH_FUNCTIONS_DIR)
-	$(INSTALL_DATA) $(FISH_COMPLETION_FUNCTION_FILENAME) $(DESTDIR)$(FISH_FUNCTIONS_DIR)/$(FISH_COMPLETION_FUNCTION_FILENAME)
+	if test -n "$(PERL)"; then \
+	  $(MKDIR_P) $(DESTDIR)$(FISH_FUNCTIONS_DIR); \
+	  $(INSTALL_DATA) $(FISH_COMPLETION_FUNCTION_FILENAME) $(DESTDIR)$(FISH_FUNCTIONS_DIR)/$(FISH_COMPLETION_FUNCTION_FILENAME) ; \
+  fi
 endif
 endif