golang: add option to skip building bootstrap

Introduce a new configuration option - GOLANG_BUILD_BOOTSTRAP - that
defaults to enabled:

- When enabled, build the local bootstrap instead of using an external
  one for host Go. If GOLANG_EXTERNAL_BOOTSTRAP_ROOT is set, skip the
  initial 1.4 step.

- When disabled, let Go auto-detect the toolchain or use the toolchain
  specified in GOLANG_EXTERNAL_BOOTSTRAP_ROOT to skip building the
  bootstrap and build host Go using that toolchain directly. Configured
  toolchain must be compatible with the current version of Go.

HOST_BUILD_DEPENDS cannot be conditional, so some Makefile juggling is
needed.

Put menu config under bootstrap only.

Remove unnecessary package-related flags from host-only bootstrap.

Signed-off-by: George Sapkin <george@sapk.in>

lang/golang/Config.in

@@ -1,33 +0,0 @@
-menu "Configuration"
-
-config GOLANG_EXTERNAL_BOOTSTRAP_ROOT
-	string "External bootstrap Go root directory"
-	default ""
-	help
-	  Path to a working Go tree (>= Go 1.4), with bin, pkg, and src
-	  subdirectories and the Go compiler at bin/go.
-
-	  If specified, the existing Go installation will be used to
-	  compile host (buildroot) Go.
-
-	  Leave blank to compile the default bootstrap Go.
-
-config GOLANG_BUILD_CACHE_DIR
-	string "Go build cache directory"
-	default ""
-	help
-	  Store the Go build cache in this directory.
-	  If not set, uses '$(TMP_DIR)/go-build'.
-
-config GOLANG_MOD_CACHE_WORLD_READABLE
-	bool "Ensure Go module cache is world-readable"
-	default n
-
-config GOLANG_SPECTRE
-	bool "Enable Spectre mitigations"
-	default n
-	depends on x86_64
-	help
-	  Currently only available for x86-64 (amd64).
-
-endmenu

lang/golang/golang-bootstrap/Config.in

@@ -0,0 +1,47 @@
+menu "Configuration"
+
+config GOLANG_EXTERNAL_BOOTSTRAP_ROOT
+	string "External bootstrap Go root directory"
+	default ""
+	help
+	  Path to a working Go tree (>= Go 1.4), with bin, pkg, and src
+	  subdirectories and the Go compiler in bin/go.
+
+	  If set, the existing Go installation will be used to compile host
+	  (buildroot) Go.
+
+	  Leave blank to compile the default bootstrap Go.
+
+config GOLANG_BUILD_BOOTSTRAP
+	bool "Build bootstrap instead of using an external one"
+	default y
+	help
+	  When enabled, build the local bootstrap instead of using an external one
+	  for host Go. If 'External bootstrap Go root directory' is set, skip the
+	  initial 1.4 step.
+
+	  When disabled, let Go auto-detect the toolchain or use the toolchain
+	  specified in 'External bootstrap Go root directory' to skip building the
+	  bootstrap and build host Go using that toolchain directly. Configured
+	  toolchain must be compatible with the current version of Go.
+
+config GOLANG_BUILD_CACHE_DIR
+	string "Go build cache directory"
+	default ""
+	help
+	  Path where Go should store its build cache.
+
+	  If not set, uses '$(TMP_DIR)/go-build'.
+
+config GOLANG_MOD_CACHE_WORLD_READABLE
+	bool "Ensure Go module cache is world-readable"
+	default n
+
+config GOLANG_SPECTRE
+	bool "Enable Spectre mitigations"
+	default n
+	depends on x86_64
+	help
+	  Currently only available for x86-64 (amd64).
+
+endmenu

lang/golang/golang-bootstrap/Makefile

@@ -28,10 +28,6 @@ PKG_LICENSE:=BSD-3-Clause
 PKG_LICENSE_FILES:=LICENSE
 PKG_CPE_ID:=cpe:/a:golang:go
 
-PKG_BUILD_DIR:=$(BUILD_DIR)/go-$(PKG_VERSION)
-PKG_BUILD_PARALLEL:=1
-PKG_BUILD_FLAGS:=no-mips16
-
 PKG_HOST_ONLY:=1
 
 HOST_BUILD_DIR:=$(BUILD_DIR_HOST)/go-$(PKG_VERSION)
@@ -119,9 +115,9 @@ ifeq ($(GO_TARGET_SPECTRE_SUPPORTED),1)
 endif
 
 define Package/golang-bootstrap
+  $(call GoPackage/GoSubMenu)
   TITLE:=Go programming language (bootstrap)
   DEPENDS:=$(GO_ARCH_DEPENDS)
-  HIDDEN:=1
 endef
 
 define Package/golang-bootstrap/description
@@ -138,7 +134,7 @@ define Package/golang-bootstrap/description
 endef
 
 define Package/golang-bootstrap/config
-  source "$(SOURCE)/../Config.in"
+	source "$(SOURCE)/Config.in"
 endef
 
 BOOTSTRAP_ROOT_DIR:=$(call qstrip,$(CONFIG_GOLANG_EXTERNAL_BOOTSTRAP_ROOT))
@@ -161,6 +157,9 @@ ifeq ($(BOOTSTRAP_ROOT_DIR),)
   $(eval $(call GoCompiler/AddProfile,Bootstrap,$(BOOTSTRAP_BUILD_DIR),,bootstrap,$(GO_HOST_OS_ARCH)))
 endif
 
+# Skip configuring and downloading stages when building is not configured
+ifeq ($(CONFIG_GOLANG_BUILD_BOOTSTRAP),y)
+
 # Bootstrap 1.17
 
 define Download/golang-bootstrap-1.17
@@ -193,6 +192,8 @@ Hooks/HostPrepare/Post+=Bootstrap-1.20/Prepare
 
 $(eval $(call GoCompiler/AddProfile,Bootstrap-1.20,$(BOOTSTRAP_1_20_BUILD_DIR),,bootstrap-1.20,$(GO_HOST_OS_ARCH)))
 
+endif
+
 # Host
 
 ifeq ($(GO_HOST_PIE_SUPPORTED),1)
@@ -202,7 +203,9 @@ endif
 # When using GO_LDFLAGS to set buildmode=pie, the PIE install suffix does not
 # apply (we also delete the std lib during Host/Install)
 
-$(eval $(call GoCompiler/AddProfile,Host,$(HOST_BUILD_DIR),$(HOST_GO_PREFIX),$(HOST_GO_VERSION_ID),$(GO_HOST_OS_ARCH)))
+ifeq ($(CONFIG_GOLANG_BUILD_BOOTSTRAP),y)
+  $(eval $(call GoCompiler/AddProfile,Host,$(HOST_BUILD_DIR),$(HOST_GO_PREFIX),$(HOST_GO_VERSION_ID),$(GO_HOST_OS_ARCH)))
+endif
 
 HOST_GO_VARS= \
 	GOHOSTARCH="$(GO_HOST_ARCH)" \
@@ -268,5 +271,11 @@ define Host/Uninstall
 	$(call GoCompiler/Host/Uninstall)
 endef
 
-$(eval $(call HostBuild))
+# Skip downloading and building final bootstrap when building is not configured
+ifeq ($(CONFIG_GOLANG_BUILD_BOOTSTRAP),y)
+  $(eval $(call HostBuild))
+else
+  host-compile:
+endif
+
 $(eval $(call BuildPackage,golang-bootstrap))

lang/golang/golang-version.mk

@@ -8,7 +8,11 @@ HOST_GO_PREFIX:=$(STAGING_DIR_HOSTPKG)
 HOST_GO_VERSION_ID:=$(GO_VERSION_MAJOR_MINOR)
 HOST_GO_ROOT:=$(HOST_GO_PREFIX)/lib/go-$(HOST_GO_VERSION_ID)
 
-BOOTSTRAP_DIR:=$(HOST_GO_PREFIX)/lib/go-$(GO_BOOTSTRAP_VERSION)
+ifeq ($(CONFIG_GOLANG_BUILD_BOOTSTRAP),y)
+  BOOTSTRAP_DIR:=$(HOST_GO_PREFIX)/lib/go-$(GO_BOOTSTRAP_VERSION)
+else
+  BOOTSTRAP_DIR:=$(call qstrip,$(CONFIG_GOLANG_EXTERNAL_BOOTSTRAP_ROOT))
+endif
 
 include ../golang-compiler.mk
 include ../golang-package.mk
@@ -57,6 +61,7 @@ define Package/$(PKG_NAME)
   TITLE+= (compiler)
   DEPENDS+= +golang$(GO_VERSION_MAJOR_MINOR)-src
   EXTRA_DEPENDS:=golang$(GO_VERSION_MAJOR_MINOR)-src (=$(PKG_VERSION)-r$(PKG_RELEASE))
+  MDEPENDS:=+golang-bootstrap
   PROVIDES:=@golang
   $(if $(filter $(GO_DEFAULT_VERSION),$(GO_VERSION_MAJOR_MINOR)),DEFAULT_VARIANT:=1)
   ALTERNATIVES:=\
@@ -71,10 +76,6 @@ define Package/$(PKG_NAME)/description
   for the Go programming language.
 endef
 
-define Package/$(PKG_NAME)/config
-  source "$(SOURCE)/../Config.in"
-endef
-
 define Package/$(PKG_NAME)-doc
   $(call Package/$(PKG_NAME)/Default)
   TITLE+= (documentation)