rust: Enable baremetal targets

Allow rust to build for baremetal targets by generating the proper target
triple, follow the format specified by rusts Triple [1], that is:

<arch>-<vendor>-<os>-<abi>

This is done automatically based on both TARGET_OS and TCLIBC.

For example, a riscv64 baremetal target triple would look like this:
riscv64gc-poky-none-elf

matching rusts own target triple for riscv64 according to platform-support [2]

[1] https://docs.rs/target-lexicon/latest/target_lexicon/struct.Triple.html
[2] https://doc.rust-lang.org/stable/rustc/platform-support.html

(From OE-Core rev: 3bff689f0c5ea73076ce0510872b0552e8660cbe)

Signed-off-by: Alejandro Enedino Hernandez Samaniego <alejandro@enedino.org>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

1 files changed, 6 insertions, 0 deletions

diff --git a/meta/classes-recipe/rust-common.bbclass b/meta/classes-recipe/rust-common.bbclass
index 3338de7502..0f72e45e8c 100644
--- a/meta/classes-recipe/rust-common.bbclass
+++ b/meta/classes-recipe/rust-common.bbclass
@@ -66,6 +66,12 @@ def rust_base_triple(d, thing):
     elif "musl" in os:
         libc = "-musl"
         os = "linux"
+    elif "elf" in os:
+        libc = "-elf"
+        os = "none"
+    elif "eabi" in os:
+        libc = "-eabi"
+        os = "none"
 
     return arch + vendor + '-' + os + libc