[PATCH] rust: fix regexp in scripts/is_rust_module.sh

[Andrea Righi <andrea.righi@canonical.com>]

nm can use "R" or "r" to show read-only data sections, but
scripts/is_rust_module.sh can only recognize "r", so with some versions
of binutils it can fail to detect if a module is a Rust module or not.

Right now we're using this script only to determine if we need to skip
BTF generation (that is disabled globally if CONFIG_RUST is enabled),
but it's still nice to fix this script to do the proper job.

Moreover, with this patch applied I can also relax the constraint of
"RUST depends on !DEBUG_INFO_BTF" and build a kernel with Rust and BTF
enabled at the same time (of course BTF generation is still skipped for
Rust modules).

Signed-off-by: Andrea Righi <andrea.righi@canonical.com>
---
 scripts/is_rust_module.sh | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/scripts/is_rust_module.sh b/scripts/is_rust_module.sh
index 28b3831a7593..464761a7cf7f 100755
--- a/scripts/is_rust_module.sh
+++ b/scripts/is_rust_module.sh
@@ -13,4 +13,4 @@ set -e
 #
 # In the future, checking for the `.comment` section may be another
 # option, see https://github.com/rust-lang/rust/pull/97550.
-${NM} "$*" | grep -qE '^[0-9a-fA-F]+ r _R[^[:space:]]+16___IS_RUST_MODULE[^[:space:]]*$'
+${NM} "$*" | grep -qE '^[0-9a-fA-F]+ [Rr] _R[^[:space:]]+16___IS_RUST_MODULE[^[:space:]]*$'
-- 
2.37.2