Separate docs task from main to install-*

[Feature #20347]

Author: hsbt

common.mk

@@ -337,7 +337,7 @@ YJIT_RUSTC_ARGS = --crate-name=yjit \
 	'--out-dir=$(CARGO_TARGET_DIR)/release/' \
 	$(top_srcdir)/yjit/src/lib.rs
 
-all: $(SHOWFLAGS) main docs
+all: $(SHOWFLAGS) main
 
 main: $(SHOWFLAGS) exts $(ENCSTATIC:static=lib)encs
 	@$(NULLCMD)
@@ -479,7 +479,7 @@ docs: srcs-doc $(DOCTARGETS)
 pkgconfig-data: $(ruby_pc)
 $(ruby_pc): $(srcdir)/template/ruby.pc.in config.status
 
-install-all: docs pre-install-all do-install-all post-install-all
+install-all: pre-install-all docs do-install-all post-install-all
 pre-install-all:: all pre-install-local pre-install-ext pre-install-gem pre-install-doc
 do-install-all: pre-install-all
 	$(INSTRUBY) --make="$(MAKE)" $(INSTRUBY_ARGS) --install=all $(INSTALL_DOC_OPTS)