subprojects: add the foreign crate

This is a cleaned up and separated version of the patches at
https://lore.kernel.org/all/20240701145853.1394967-4-pbonzini@redhat.com/
https://lore.kernel.org/all/20240701145853.1394967-5-pbonzini@redhat.com/

Its first user will be the Error bindings; for example a QEMU Error ** can be
converted to a Rust Option using

     unsafe { Option::<Error>::from_foreign(c_error) }

Reviewed-by: Zhao Liu <zhao1.liu@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

subprojects/.gitignore

@@ -11,6 +11,7 @@
 /bilge-0.2.0
 /bilge-impl-0.2.0
 /either-1.12.0
+/foreign-0.3.1
 /itertools-0.11.0
 /libc-0.2.162
 /proc-macro-error-1.0.4

subprojects/foreign-0.3-rs.wrap

@@ -0,0 +1,7 @@
+[wrap-file]
+directory = foreign-0.3.1
+source_url = https://crates.io/api/v1/crates/foreign/0.3.1/download
+source_filename = foreign-0.3.1.tar.gz
+source_hash = 17ca1b5be8c9d320daf386f1809c7acc0cb09accbae795c2001953fa50585846
+#method = cargo
+patch_directory = foreign-0.3-rs

subprojects/packagefiles/foreign-0.3-rs/meson.build

@@ -0,0 +1,26 @@
+project('foreign-0.3-rs', 'rust',
+  meson_version: '>=1.5.0',
+  version: '0.2.0',
+  license: 'MIT OR Apache-2.0',
+  default_options: [])
+
+subproject('libc-0.2-rs', required: true)
+libc_rs = dependency('libc-0.2-rs')
+
+_foreign_rs = static_library(
+  'foreign',
+  files('src/lib.rs'),
+  gnu_symbol_visibility: 'hidden',
+  override_options: ['rust_std=2021', 'build.rust_std=2021'],
+  rust_abi: 'rust',
+  rust_args: [
+    '--cap-lints', 'allow',
+  ],
+  dependencies: [libc_rs],
+)
+
+foreign_dep = declare_dependency(
+  link_with: _foreign_rs,
+)
+
+meson.override_dependency('foreign-0.3-rs', foreign_dep)