rust: Use awk instead of recent xargs

[ Upstream commit 45f97e63 ]

`awk` is already required by the kernel build, and the `xargs` feature
used in current Rust detection is not present in all `xargs` (notably,
toybox based xargs, used in the Android kernel build).

Signed-off-by: Matthew Maurer <mmaurer@google.com>
Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Tested-by: Alice Ryhl <aliceryhl@google.com>
Reviewed-by: Martin Rodriguez Reboredo <yakoyoku@gmail.com>
Link: https://lore.kernel.org/r/20230928205045.2375899-1-mmaurer@google.com


Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
Stable-dep-of: b8673d56 ("rust: kbuild: fix export of bss symbols")
Signed-off-by: Sasha Levin <sashal@kernel.org>