package/rust: install rustc and rust-std built by Buildroot

The test TestRust is currently broken with ripgrep package with
the following error:

error[E0514]: found crate `core` compiled by an incompatible version of rustc
  |
  = help: please recompile that crate using this compiler (rustc 1.58.1) (consider running `cargo clean` first)
  = note: the following crate versions were found:
          crate `core` compiled by rustc 1.58.1 (db9d1b20b 2022-01-20): TestRust/host/lib/rustlib/x86_64-unknown-linux-gnu/lib/libcore-6cfcec236d576603.rlib

error[E0514]: found crate `std` compiled by an incompatible version of rustc

The problem is not really a cross-compilation issue (we are building
for an armv7 target on x86_64 host) but a problem with rust-std libraries
(rlib).

We can notice that "rustc 1.58.1 (db9d1b20b 2022-01-20)" is the same
version as the prebuilt rustc used to bootstrap the build:

TestRust/host/bin/rustc --version
rustc 1.58.1

TestRustBin/host/bin/rustc --version
rustc 1.58.1 (db9d1b20b 2022-01-20)

Indeed we are using host-rust-bin to bootstrap the host-rust compiler
package built by Buildroot. The problem is that the
libcore-6cfcec236d576603.rlib file come from host-rust-bin (rust-std)
and is not removed before installing host-rust built by Buildroot.

We actually spent a lot of time to build host-rust with rust-std
and forget to install this important library HOST_DIR.

Looking at the host-rust build directory we can notice two installer
script "install.sh" (the same scripts used to install host-rust-bin):

TestRust/build/host-rust-1.58.1/build/tmp/tarball/rust/x86_64-unknown-linux-gnu/rust-1.58.1-x86_64-unknown-linux-gnu/install.sh
TestRust/build/host-rust-1.58.1/build/tmp/tarball/rust-std/armv7-unknown-linux-gnueabihf/rust-std-1.58.1-armv7-unknown-linux-gnueabihf/install.sh

The "tarball" directory is generated by the "python x.py dist" during
the install step, we have to keep it.

Replace "python x.py install" by theses two install scripts.
Installing rust-std with the install.sh script replace the rust-std
libraries installed by host-rust-bin.

Fixes:
https://gitlab.com/buildroot.org/buildroot/-/jobs/2116202544

Signed-off-by: Romain Naour <romain.naour@gmail.com>
Cc: Eric Le Bihan <eric.le.bihan.dev@free.fr>
[Arnout: remove redundant parenthesis; only use a variable for the
common install opts]
Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>
(cherry picked from commit 15682493918ead960d326bf24763e9b5d8d331d9)
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/rust/rust.mk

@@ -67,9 +67,26 @@ define HOST_RUST_BUILD_CMDS
 	cd $(@D); $(HOST_MAKE_ENV) $(HOST_DIR)/bin/python$(PYTHON3_VERSION_MAJOR) x.py build
 endef
 
+HOST_RUST_INSTALL_OPTS = \
+	--prefix=$(HOST_DIR) \
+	--disable-ldconfig
+
+define HOST_RUST_INSTALL_RUSTC
+	cd $(@D)/build/tmp/tarball/rust/$(RUSTC_HOST_NAME)/rust-$(RUST_VERSION)-$(RUSTC_HOST_NAME); \
+		./install.sh $(HOST_RUST_INSTALL_OPTS) --components=rustc,cargo,rust-std-$(RUSTC_HOST_NAME)
+endef
+
+ifeq ($(BR2_PACKAGE_HOST_RUSTC_TARGET_ARCH_SUPPORTS),y)
+define HOST_RUST_INSTALL_LIBSTD_TARGET
+	cd $(@D)/build/tmp/tarball/rust-std/$(RUSTC_TARGET_NAME)/rust-std-$(RUST_VERSION)-$(RUSTC_TARGET_NAME); \
+		./install.sh $(HOST_RUST_INSTALL_OPTS)
+endef
+endif
+
 define HOST_RUST_INSTALL_CMDS
 	cd $(@D); $(HOST_MAKE_ENV) $(HOST_DIR)/bin/python$(PYTHON3_VERSION_MAJOR) x.py dist
-	cd $(@D); $(HOST_MAKE_ENV) $(HOST_DIR)/bin/python$(PYTHON3_VERSION_MAJOR) x.py install
+	$(HOST_RUST_INSTALL_RUSTC)
+	$(HOST_RUST_INSTALL_LIBSTD_TARGET)
 endef
 
 $(eval $(host-generic-package))