mk: Simplify how prepare.mk, install.mk, and dist.mk deal with stages

The only stage that can be installed from is 2 everywhere but windows,
3 on windows.

Closes #12799

mk/dist.mk

@@ -65,8 +65,6 @@ $(PKG_EXE): rust.iss modpath.iss LICENSE.txt rust-logo.ico \
 dist-prepare-win: PREPARE_HOST=$(CFG_BUILD)
 dist-prepare-win: PREPARE_TARGETS=$(CFG_BUILD)
 dist-prepare-win: PREPARE_DEST_DIR=tmp/dist/win
-# On windows we're using stage3, unlike Unix...
-dist-prepare-win: PREPARE_STAGE=3
 dist-prepare-win: PREPARE_DIR_CMD=$(DEFAULT_PREPARE_DIR_CMD)
 dist-prepare-win: PREPARE_BIN_CMD=$(DEFAULT_PREPARE_BIN_CMD)
 dist-prepare-win: PREPARE_LIB_CMD=$(DEFAULT_PREPARE_LIB_CMD)
@@ -135,7 +133,6 @@ ifeq ($(CFG_OSTYPE), apple-darwin)
 dist-prepare-osx: PREPARE_HOST=$(CFG_BUILD)
 dist-prepare-osx: PREPARE_TARGETS=$(CFG_BUILD)
 dist-prepare-osx: PREPARE_DEST_DIR=tmp/dist/pkgroot
-dist-prepare-osx: PREPARE_STAGE=2
 dist-prepare-osx: PREPARE_DIR_CMD=$(DEFAULT_PREPARE_DIR_CMD)
 dist-prepare-osx: PREPARE_BIN_CMD=$(DEFAULT_PREPARE_BIN_CMD)
 dist-prepare-osx: PREPARE_LIB_CMD=$(DEFAULT_PREPARE_LIB_CMD)
@@ -165,7 +162,6 @@ dist-tar-bins: $(foreach host,$(CFG_HOST),dist/$(PKG_DIR)-$(host).tar.gz)
 define DEF_INSTALLER
 dist-install-dir-$(1): PREPARE_HOST=$(1)
 dist-install-dir-$(1): PREPARE_TARGETS=$(1)
-dist-install-dir-$(1): PREPARE_STAGE=2
 dist-install-dir-$(1): PREPARE_DEST_DIR=tmp/dist/$$(PKG_DIR)-$(1)
 dist-install-dir-$(1): PREPARE_DIR_CMD=$(DEFAULT_PREPARE_DIR_CMD)
 dist-install-dir-$(1): PREPARE_BIN_CMD=$(DEFAULT_PREPARE_BIN_CMD)

mk/install.mk

@@ -13,11 +13,10 @@
 # mirror of the installation directory structure.
 
 # The stage we install from
-ISTAGE = 2
+ISTAGE = $(PREPARE_STAGE)
 
 install: PREPARE_HOST=$(CFG_BUILD)
 install: PREPARE_TARGETS=$(CFG_TARGET)
-install: PREPARE_STAGE=$(ISTAGE)
 install: PREPARE_DIR_CMD=$(DEFAULT_PREPARE_DIR_CMD)
 install: PREPARE_BIN_CMD=$(DEFAULT_PREPARE_BIN_CMD)
 install: PREPARE_LIB_CMD=$(DEFAULT_PREPARE_LIB_CMD)

mk/prepare.mk

@@ -20,7 +20,14 @@
 #   PREPARE_TARGETS - the target triples, space separated
 #   PREPARE_DEST_DIR - the directory to put the image
 
-prepare: PREPARE_STAGE=2
+
+# On windows we install from stage3, but on unix only stage2
+ifdef CFG_WINDOWSY_$(CFG_BUILD)
+PREPARE_STAGE=3
+else
+PREPARE_STAGE=2
+endif
+
 prepare: PREPARE_DIR_CMD=$(DEFAULT_PREPARE_DIR_CMD)
 prepare: PREPARE_BIN_CMD=$(DEFAULT_PREPARE_BIN_CMD)
 prepare: PREPARE_LIB_CMD=$(DEFAULT_PREPARE_LIB_CMD)
@@ -43,15 +50,6 @@ DEFAULT_PREPARE_BIN_CMD = install -m755
 DEFAULT_PREPARE_LIB_CMD = install -m644
 DEFAULT_PREPARE_MAN_CMD = install -m644
 
-# On windows we install from stage3, but on unix only stage2
-# Because of the way these rules are organized, preparing from any
-# stage requires all these stages to be built
-ifdef CFG_WINDOWSY_$(CFG_BUILD)
-PREPARE_STAGES=3
-else
-PREPARE_STAGES=2
-endif
-
 # Create a directory
 # $(1) is the directory
 define PREPARE_DIR
@@ -102,9 +100,8 @@ prepare-host: prepare-host-tools
 
 prepare-host-tools: \
         $(foreach tool, $(PREPARE_TOOLS),\
-          $(foreach stage,$(PREPARE_STAGES),\
-            $(foreach host,$(CFG_HOST),\
-              prepare-host-tool-$(tool)-$(stage)-$(host))))
+          $(foreach host,$(CFG_HOST),\
+            prepare-host-tool-$(tool)-$(PREPARE_STAGE)-$(host)))
 
 prepare-host-dirs: prepare-maybe-clean
 	$(call PREPARE_DIR,$(PREPARE_DEST_BIN_DIR))
@@ -128,9 +125,8 @@ prepare-host-tool-$(1)-$(2)-$(3): prepare-maybe-clean \
 endef
 
 $(foreach tool,$(PREPARE_TOOLS),\
-  $(foreach stage,$(PREPARE_STAGES),\
-    $(foreach host,$(CFG_HOST),\
-        $(eval $(call DEF_PREPARE_HOST_TOOL,$(tool),$(stage),$(host))))))
+  $(foreach host,$(CFG_HOST),\
+      $(eval $(call DEF_PREPARE_HOST_TOOL,$(tool),$(PREPARE_STAGE),$(host)))))
 
 # For host libraries only install dylibs, not rlibs since the host libs are only
 # used to support rustc and rustc uses dynamic linking
@@ -151,15 +147,13 @@ prepare-host-lib-$(1)-$(2)-$(3): prepare-maybe-clean \
 endef
 
 $(foreach lib,$(CRATES),\
-  $(foreach stage,$(PREPARE_STAGES),\
-    $(foreach host,$(CFG_HOST),\
-      $(eval $(call DEF_PREPARE_HOST_LIB,$(lib),$(stage),$(host))))))
+  $(foreach host,$(CFG_HOST),\
+    $(eval $(call DEF_PREPARE_HOST_LIB,$(lib),$(PREPARE_STAGE),$(host)))))
 
 prepare-targets:\
         $(foreach host,$(CFG_HOST),\
            $(foreach target,$(CFG_TARGET),\
-             $(foreach stage,$(PREPARE_STAGES),\
-               prepare-target-$(target)-host-$(host)-$(stage))))
+             prepare-target-$(target)-host-$(host)-$(PREPARE_STAGE)))
 
 # $(1) is stage
 # $(2) is target
@@ -194,8 +188,7 @@ endef
 
 $(foreach host,$(CFG_HOST),\
   $(foreach target,$(CFG_TARGET), \
-    $(foreach stage,$(PREPARE_STAGES),\
-      $(eval $(call DEF_PREPARE_TARGET_N,$(stage),$(target),$(host))))))
+    $(eval $(call DEF_PREPARE_TARGET_N,$(PREPARE_STAGE),$(target),$(host)))))
 
 prepare-maybe-clean:
 	$(if $(findstring true,$(PREPARE_CLEAN)),\