gnu: rust: Add support for building 32-bit packages on 64-bit hosts.

* gnu/packages/rust.scm (rust-bootstrap, rust-1.23): Use
nix-system->gnu-triplet to determine the system type.
(rust-1.19): Use readelf instead of nm in the atomic-lock-free test.
(rust-1.23): Disable the cargo_test_env test. Disable parallel execution of
tests.

Signed-off-by: Ludovic Courtès <ludo@gnu.org>

gnu/packages/rust.scm

@@ -63,14 +63,23 @@
   (package
     (name "rust-bootstrap")
     (version "1.22.1")
-    (source (origin
+    (source #f)
+    (build-system gnu-build-system)
+    (native-inputs
+     `(("patchelf" ,patchelf)))
+    (inputs
+     `(("gcc" ,(canonical-package gcc))
+       ("gcc:lib" ,(canonical-package gcc) "lib")
+       ("zlib" ,zlib)
+       ("source"
+        ,(origin
            (method url-fetch)
            (uri (string-append
                  "https://static.rust-lang.org/dist/"
-                    "rust-" version "-" %host-type ".tar.gz"))
+                 "rust-" version "-" (nix-system->gnu-triplet) ".tar.gz"))
            (sha256
             (base32
-                (match %host-type
+             (match (nix-system->gnu-triplet)
                ("i686-unknown-linux-gnu"
                 "15zqbx86nm13d5vq2gm69b7av4vg479f74b5by64hs3bcwwm08pr")
                ("x86_64-unknown-linux-gnu"
@@ -81,14 +90,7 @@
                 "0z6m9m1rx4d96nvybbfmpscq4dv616m615ijy16d5wh2vx0p4na8")
                ("mips64el-unknown-linux-gnuabi64"
                 "07k4pcv7jvfa48cscdj8752lby7m7xdl88v3a6na1vs675lhgja2")
-                  (_ ""))))))
+               (_ ""))))))))
-    (build-system gnu-build-system)
-    (native-inputs
-     `(("patchelf" ,patchelf)))
-    (inputs
-     `(("gcc" ,(canonical-package gcc))
-       ("gcc:lib" ,(canonical-package gcc) "lib")
-       ("zlib" ,zlib)))
     (outputs '("out" "cargo"))
     (arguments
      `(#:tests? #f
@@ -117,7 +119,7 @@
                (invoke "bash" "install.sh"
                         (string-append "--prefix=" out)
                         (string-append "--components=rustc,"
-                                       "rust-std-" %host-type))
+                                       "rust-std-" ,(nix-system->gnu-triplet)))
                ;; Instal cargo
                (invoke "bash" "install.sh"
                         (string-append "--prefix=" cargo-out)
@@ -196,6 +198,12 @@ in turn be used to build the final Rust.")
                  ;; This test is known to fail on aarch64 and powerpc64le:
                  ;; https://github.com/rust-lang/rust/issues/45410
                  (("fn test_loading_cosine") "#[ignore]\nfn test_loading_cosine"))
+               ;; nm doesn't recognize the file format because of the
+               ;; nonstandard sections used by the Rust compiler, but readelf
+               ;; ignores them.
+               (substitute* "src/test/run-make/atomic-lock-free/Makefile"
+                 (("\tnm ")
+                  "\treadelf -c "))
                #t)))
          (add-after 'patch-source-shebangs 'patch-cargo-checksums
            (lambda* _
@@ -386,6 +394,10 @@ safety and thread safety guarantees.")
                (substitute* "src/tools/cargo/tests/death.rs"
                 ;; This is stuck when built in container.
                 (("fn ctrl_c_kills_everyone") "#[ignore]\nfn ctrl_c_kills_everyone"))
+               ;; Prints test output in the wrong order when built on
+               ;; i686-linux.
+               (substitute* "src/tools/cargo/tests/test.rs"
+                 (("fn cargo_test_env") "#[ignore]\nfn cargo_test_env"))
                #t))
            (add-after 'patch-cargo-tests 'fix-mtime-bug
              (lambda* _
@@ -433,7 +445,7 @@ rpath = true
 # codegen/mainsubprogram.rs and codegen/mainsubprogramstart.rs
 # This tests required patched LLVM
 codegen-tests = false
-[target." %host-type "]
+[target." ,(nix-system->gnu-triplet) "]
 llvm-config = \"" llvm "/bin/llvm-config" "\"
 cc = \"" gcc "/bin/gcc" "\"
 cxx = \"" gcc "/bin/g++" "\"
@@ -456,8 +468,10 @@ jemalloc = \"" jemalloc "/lib/libjemalloc_pic.a" "\"
              (invoke "./x.py" "build" "src/tools/cargo")))
          (replace 'check
            (lambda* _
-             (invoke "./x.py" "test")
+             ;; Disable parallel execution to prevent EAGAIN errors when
-             (invoke "./x.py" "test" "src/tools/cargo")))
+             ;; running tests.
+             (invoke "./x.py" "-j1" "test")
+             (invoke "./x.py" "-j1" "test" "src/tools/cargo")))
          (replace 'install
            (lambda* (#:key outputs #:allow-other-keys)
              (invoke "./x.py" "install")