rust-target-config: fix nativesdk-libstd-rs build with baremetal

If TCLIBC='baremetal' is set in local.conf, nativesdk-libstd-rs build fails
with:

| error[E0412]: cannot find type `c_char` in the crate root
|   --> /usr/src/debug/libstd-rs/1.75.0/rustc-1.75.0-src/vendor/libc/src/unix/mod.rs:56:29
|    |
| 6  | pub type c_schar = i8;
|    | ---------------------- similarly named type alias `c_schar` defined here
| ...
| 56 |         pub gr_name: *mut ::c_char,
|    |                             ^^^^^^

This happens because rust_gen_target() sets os="none" when TCLIBC is
'baremetal' - even for nativesdk targets. However, nativesdk packages are
built against glibc, so the correct 'os' value should be "linux".

Fix this by setting the os field based on {TARGET,HOST,BUILD}_OS variables,
as it is already done in rust_base_triple(), instead of relying on TCLIBC.

(From OE-Core rev: 4c3f321304f2aa8b75cb58699b59fea80a23690c)

Signed-off-by: Ovidiu Panait <ovidiu.panait@windriver.com>
Signed-off-by: Mathieu Dubois-Briand <mathieu.dubois-briand@bootlin.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
(master rev: 3eaf2cd5647585a1e6df03fc20e2753da27bb692) -- backport
Signed-off-by: Stefan Ghinea <stefan.ghinea@windriver.com>
Signed-off-by: Steve Sakoman <steve@sakoman.com>

1 files changed, 2 insertions, 1 deletions

diff --git a/meta/classes-recipe/rust-target-config.bbclass b/meta/classes-recipe/rust-target-config.bbclass
index 1bd7626bd8..31b4bd9afd 100644
--- a/meta/classes-recipe/rust-target-config.bbclass
+++ b/meta/classes-recipe/rust-target-config.bbclass
@@ -329,6 +329,7 @@ def rust_gen_target(d, thing, wd, arch):
     sys = d.getVar('{}_SYS'.format(thing))
     prefix = d.getVar('{}_PREFIX'.format(thing))
     rustsys = d.getVar('RUST_{}_SYS'.format(thing))
+    os = d.getVar('{}_OS'.format(thing))
 
     abi = None
     cpu = "generic"
@@ -368,7 +369,7 @@ def rust_gen_target(d, thing, wd, arch):
     tspec['target-c-int-width'] = d.getVarFlag('TARGET_C_INT_WIDTH', arch_abi)
     tspec['target-endian'] = d.getVarFlag('TARGET_ENDIAN', arch_abi)
     tspec['arch'] = arch_to_rust_target_arch(rust_arch)
-    if "baremetal" in d.getVar('TCLIBC'):
+    if "elf" in os:
         tspec['os'] = "none"
     else:
         tspec['os'] = "linux"