rust: Set rustflags by environment variable

In order to use $(RUSTC_TARGET_ARCH) in HOST_BUILD_DIR, the line to
include rust-values.mk in the Rust makefile was moved in
f489e019ac, causing it to be included
before package.mk is included.

This had the side effect of preventing "-lssp_nonshared" from being
added to RUSTC_LDFLAGS, because PKG_SSP is indirectly set by package.mk
(package.mk includes hardening.mk, hardening.mk sets PKG_SSP).

There is a deeper issue; it is the Rust package's PKG_SSP value that
causes RUSTC_LDFLAGS to be set and written to the Cargo config file. For
packages that use Rust to build, their PKG_SSP value does not affect the
linker flag.

This sets rustflags with the RUSTFLAGS environment variable, instead of
writing the value to the Cargo config file, allowing PKG_SSP from the
package being built to be used and for the package being built to modify
the rustflags used.

This also:

* Fix "-lssp_nonshared" being added to TARGET_CFLAGS instead of
  RUSTC_LDFLAGS, when CONFIG_PKG_CC_STACKPROTECTOR_STRONG is set.

* Remove the use of $(RUSTC_TARGET_ARCH) in HOST_BUILD_DIR and move the
  include line for rust-values.mk back to after package.mk.

  Since the host build directory was moved under the target build
  directory in efdbac38dc, it is no longer
  necessary to separate build directories with RUSTC_TARGET_ARCH;
  $(BUILD_DIR) already separates build directories by target.

* Add BUILDONLY:=1, as the Rust package does not build a target package.

* Install the Cargo config file as "config.toml" instead of "config", as
  this is the preferred form[1].

* Rename RUST_CFLAGS to RUSTC_CFLAGS and CONFIG_HOST_SUFFIX to
  RUSTC_HOST_SUFFIX, for consistency.

* Allow CARGO_VARS to be set before rust-values.mk is included.

[1]: https://doc.rust-lang.org/cargo/reference/config.html#hierarchical-structure

Fixes: f489e019ac ("rust: compile host package per target")
Fixes: 83785a7ce0 ("rust-lang: Add the rust language support")
Fixes: https://github.com/openwrt/packages/issues/22133

Signed-off-by: Jeffery To <jeffery.to@gmail.com>

lang/rust/Makefile

@@ -3,16 +3,15 @@
 # Copyright (C) 2023 Luca Barbato and Donald Hoskins
 
 include $(TOPDIR)/rules.mk
-include ./rust-values.mk
 
 PKG_NAME:=rust
 PKG_VERSION:=1.72.0
-PKG_RELEASE:=1
+PKG_RELEASE:=2
 
 PKG_SOURCE:=rustc-$(PKG_VERSION)-src.tar.gz
 PKG_SOURCE_URL:=https://static.rust-lang.org/dist/
 PKG_HASH:=ea9d61bbb51d76b6ea681156f69f0e0596b59722f04414b01c6e100b4b5be3a1
-HOST_BUILD_DIR:=$(BUILD_DIR)/host/rust-$(RUSTC_TARGET_ARCH)/rustc-$(PKG_VERSION)-src
+HOST_BUILD_DIR:=$(BUILD_DIR)/host/rustc-$(PKG_VERSION)-src
 
 PKG_MAINTAINER:=Luca Barbato <lu_zero@luminem.org>
 PKG_LICENSE:=Apache-2.0 MIT
@@ -23,6 +22,7 @@ PKG_HOST_ONLY:=1
 
 include $(INCLUDE_DIR)/host-build.mk
 include $(INCLUDE_DIR)/package.mk
+include ./rust-values.mk
 
 define Package/rust
   SECTION:=lang
@@ -31,6 +31,7 @@ define Package/rust
   TITLE:=Rust Programming Language Compiler
   URL:=https://www.rust-lang.org/
   DEPENDS:=$(RUST_ARCH_DEPENDS)
+  BUILDONLY:=1
 endef
 
 define Package/rust/description
@@ -95,8 +96,7 @@ define Host/Install
 		\
 		sed -e 's|@RUSTC_TARGET_ARCH@|$(RUSTC_TARGET_ARCH)|g' \
 		    -e 's|@TARGET_CC_NOCACHE@|$(TARGET_CC_NOCACHE)|g' \
-		    -e 's|@RUSTC_LDFLAGS@|$(RUSTC_LDFLAGS)|g' \
-			$(CURDIR)/files/cargo-config > $(CARGO_HOME)/config ; \
+			$(CURDIR)/files/cargo-config > $(CARGO_HOME)/config.toml ; \
 	)
 endef
 

lang/rust/files/cargo-config

@@ -1,6 +1,5 @@
 [target.@RUSTC_TARGET_ARCH@]
 linker = "@TARGET_CC_NOCACHE@"
-rustflags = ["-Ctarget-feature=-crt-static", "-Clink-args=@RUSTC_LDFLAGS@"]
 
 [profile.stripped]
 inherits = "release"

lang/rust/rust-package.mk

@@ -22,9 +22,10 @@ define Build/Compile/Cargo
 		cd $(PKG_BUILD_DIR) ; \
 		export PATH="$(CARGO_HOME)/bin:$(PATH)" ; \
 		CARGO_HOME=$(CARGO_HOME) \
-		TARGET_CFLAGS="$(TARGET_CFLAGS) $(RUST_CFLAGS)" \
+		TARGET_CFLAGS="$(TARGET_CFLAGS) $(RUSTC_CFLAGS)" \
 		TARGET_CC=$(TARGET_CC_NOCACHE) \
 		CC=$(HOSTCC_NOCACHE) \
+		RUSTFLAGS="$(CARGO_RUSTFLAGS)" \
 		$(CARGO_VARS) \
 		cargo install -v \
 			--profile stripped \

lang/rust/rust-values.mk

@@ -3,24 +3,26 @@
 # Copyright (C) 2023 Luca Barbato and Donald Hoskins
 
 # Rust Environmental Vars
-CONFIG_HOST_SUFFIX:=$(word 4, $(subst -, ,$(GNU_HOST_NAME)))
-RUSTC_HOST_ARCH:=$(HOST_ARCH)-unknown-linux-$(CONFIG_HOST_SUFFIX)
+RUSTC_HOST_SUFFIX:=$(word 4, $(subst -, ,$(GNU_HOST_NAME)))
+RUSTC_HOST_ARCH:=$(HOST_ARCH)-unknown-linux-$(RUSTC_HOST_SUFFIX)
 CARGO_HOME:=$(STAGING_DIR)/host/cargo
-CARGO_VARS:=
+CARGO_VARS?=
 
 ifeq ($(CONFIG_USE_MUSL),y)
-# Force linking of the SSP library for musl
-ifdef CONFIG_PKG_CC_STACKPROTECTOR_REGULAR
-  ifeq ($(strip $(PKG_SSP)),1)
-    RUSTC_LDFLAGS += -lssp_nonshared
+  # Force linking of the SSP library for musl
+  ifdef CONFIG_PKG_CC_STACKPROTECTOR_REGULAR
+    ifeq ($(strip $(PKG_SSP)),1)
+      RUSTC_LDFLAGS+=-lssp_nonshared
+    endif
+  endif
+  ifdef CONFIG_PKG_CC_STACKPROTECTOR_STRONG
+    ifeq ($(strip $(PKG_SSP)),1)
+      RUSTC_LDFLAGS+=-lssp_nonshared
+    endif
   endif
 endif
-ifdef CONFIG_PKG_CC_STACKPROTECTOR_STRONG
-  ifeq ($(strip $(PKG_SSP)),1)
-    TARGET_CFLAGS += -lssp_nonshared
-  endif
-endif
-endif
+
+CARGO_RUSTFLAGS+=-Ctarget-feature=-crt-static $(RUSTC_LDFLAGS)
 
 ifeq ($(HOST_OS),Darwin)
   ifeq ($(HOST_ARCH),arm64)
@@ -55,7 +57,7 @@ ifeq ($(ARCH),arm)
 endif
 
 ifeq ($(ARCH),aarch64)
-    RUST_CFLAGS:=-mno-outline-atomics
+    RUSTC_CFLAGS:=-mno-outline-atomics
 endif
 
 # Support only a subset for now.