Add rust-std-static-wasm32-unknown-unknown.

This change is partly based on an older pull request:
https://src.fedoraproject.org/rpms/rust/pull-request/6

Co-authored-by: Ivan Mironov <mironov.ivan@gmail.com>

0001-Use-lld-provided-by-system-for-wasm.patch

@@ -0,0 +1,26 @@
+From 1a6307bbf7972aa2ce89a213bad6f26b6325a59c Mon Sep 17 00:00:00 2001
+From: Ivan Mironov <mironov.ivan@gmail.com>
+Date: Sun, 8 Dec 2019 17:23:08 +0500
+Subject: [PATCH] Use lld provided by system for wasm
+
+---
+ compiler/rustc_target/src/spec/wasm32_base.rs | 3 +--
+ 1 file changed, 1 insertion(+), 2 deletions(-)
+
+diff --git a/compiler/rustc_target/src/spec/wasm32_base.rs b/compiler/rustc_target/src/spec/wasm32_base.rs
+index bfef3d37228f..0ecb29248fe2 100644
+--- a/compiler/rustc_target/src/spec/wasm32_base.rs
++++ b/compiler/rustc_target/src/spec/wasm32_base.rs
+@@ -97,8 +97,7 @@ pub fn options() -> TargetOptions {
+         // arguments just yet
+         limit_rdylib_exports: false,
+ 
+-        // we use the LLD shipped with the Rust toolchain by default
+-        linker: Some("rust-lld".to_owned()),
++        linker: Some("lld".to_owned()),
+         lld_flavor: LldFlavor::Wasm,
+ 
+         // No need for indirection here, simd types can always be passed by
+-- 
+2.31.1
+

rust.spec

@@ -17,6 +17,15 @@
 # Only the specified arches will use bootstrap binaries.
 #global bootstrap_arches %%{rust_arches}
 
+# Define a space-separated list of targets to ship rust-std-static-$triple for
+# cross-compilation. The packages are noarch, but they're not fully
+# reproducible between hosts, so only x86_64 actually builds it.
+%ifarch x86_64
+%if 0%{?fedora}
+%global cross_targets wasm32-unknown-unknown
+%endif
+%endif
+
 # Using llvm-static may be helpful as an opt-in, e.g. to aid LLVM rebases.
 %bcond_with llvm_static
 
@@ -71,6 +80,9 @@ Source0:        https://static.rust-lang.org/dist/%{rustc_package}.tar.xz
 # https://github.com/rust-lang/rust/issues/80810#issuecomment-781784032
 Patch1:         0001-Revert-Auto-merge-of-79547.patch
 
+# By default, rust tries to use "rust-lld" as a linker for WebAssembly.
+Patch2:         0001-Use-lld-provided-by-system-for-wasm.patch
+
 ### RHEL-specific patches below ###
 
 # Disable cargo->libgit2->libssh2 on RHEL, as it's not approved for FIPS (rhbz1732949)
@@ -235,6 +247,19 @@ Requires:       /usr/bin/cc
 %endif
 %endif
 
+# We're going to override --libdir when configuring to get rustlib into a
+# common path, but we'll fix the shared libraries during install.
+%global common_libdir %{_prefix}/lib
+%global rustlibdir %{common_libdir}/rustlib
+
+%if %defined cross_targets
+# brp-strip-static-archive breaks the archive index for wasm
+%global __os_install_post \
+%__os_install_post \
+find %{buildroot}%{rustlibdir} -type f -path '*/wasm*/lib/*.rlib' -exec ranlib '{}' ';' \
+%{nil}
+%endif
+
 %description
 Rust is a systems programming language that runs blazingly fast, prevents
 segfaults, and guarantees thread safety.
@@ -249,6 +274,32 @@ Summary:        Standard library for Rust
 This package includes the standard libraries for building applications
 written in Rust.
 
+%if %defined cross_targets
+%{lua: do
+  for triple in string.gmatch(rpm.expand("%{cross_targets}"), "%S+") do
+    local requires = rpm.expand("Requires: rust = %{version}-%{release}")
+    if string.sub(triple, 1, 4) == "wasm" then
+      requires = requires .. "\nRequires: lld >= 8.0"
+    end
+    local subs = {
+      triple = triple,
+      requires = requires,
+    }
+    local s = string.gsub([[
+%package std-static-{{triple}}
+Summary:        Standard library for Rust
+BuildArch:      noarch
+{{requires}}
+
+%description std-static-{{triple}}
+This package includes the standard libraries for building applications
+written in Rust for the {{triple}} target.
+]], "{{(%w+)}}", subs)
+    print(s)
+  end
+end}
+%endif
+
 
 %package debugger-common
 Summary:        Common debugger pretty printers for Rust
@@ -406,6 +457,7 @@ test -f '%{local_rust_root}/bin/rustc'
 %setup -q -n %{rustc_package}
 
 %patch1 -p1
+%patch2 -p1
 
 %if %with disabled_libssh2
 %patch100 -p1
@@ -491,11 +543,6 @@ find -name '*.rs' -type f -perm /111 -exec chmod -v -x '{}' '+'
 %build
 export %{rust_env}
 
-# We're going to override --libdir when configuring to get rustlib into a
-# common path, but we'll fix the shared libraries during install.
-%global common_libdir %{_prefix}/lib
-%global rustlibdir %{common_libdir}/rustlib
-
 %ifarch %{arm} %{ix86} s390x
 # full debuginfo is exhausting memory; just do libstd for now
 # https://github.com/rust-lang/rust/issues/45854
@@ -540,12 +587,23 @@ fi
 %{python} ./x.py build -j "$ncpus" --stage 2
 %{python} ./x.py doc --stage 2
 
+%if %defined cross_targets
+for triple in %{cross_targets}; do
+  %{python} ./x.py build --stage 2 --target=$triple std
+done
+%endif
 
 %install
 export %{rust_env}
 
 DESTDIR=%{buildroot} %{python} ./x.py install
 
+%if %defined cross_targets
+for triple in %{cross_targets}; do
+  DESTDIR=%{buildroot} %{python} ./x.py install --target=$triple std
+done
+%endif
+
 # Make sure the shared libraries are in the proper libdir
 %if "%{_libdir}" != "%{common_libdir}"
 mkdir -p %{buildroot}%{_libdir}
@@ -648,6 +706,26 @@ export %{rust_env}
 %{rustlibdir}/%{rust_triple}/lib/*.rlib
 
 
+%if %defined cross_targets
+%{lua: do
+  for triple in string.gmatch(rpm.expand("%{cross_targets}"), "%S+") do
+    local subs = {
+      triple = triple,
+      rustlibdir = rpm.expand("%{rustlibdir}"),
+    }
+    local s = string.gsub([[
+%files std-static-{{triple}}
+%dir {{rustlibdir}}
+%dir {{rustlibdir}}/{{triple}}
+%dir {{rustlibdir}}/{{triple}}/lib
+{{rustlibdir}}/{{triple}}/lib/*.rlib
+]], "{{(%w+)}}", subs)
+    print(s)
+  end
+end}
+%endif
+
+
 %files debugger-common
 %dir %{rustlibdir}
 %dir %{rustlibdir}/etc
@@ -733,6 +811,7 @@ export %{rust_env}
 %changelog
 * Wed Jun 02 2021 Josh Stone <jistone@redhat.com> - 1.52.1-2
 - Set rust.codegen-units-std=1 for all targets again.
+- Add rust-std-static-wasm32-unknown-unknown.
 
 * Mon May 10 2021 Josh Stone <jistone@redhat.com> - 1.52.1-1
 - Update to 1.52.1.