kbuild: rust_is_available: fix confusion when a version appears in the path

BugLink: https://bugs.launchpad.net/bugs/2042884

[ Upstream commit 9eb7e20e0c5cd069457845f965b3e8a7d736ecb7 ]

`bindgen`'s output for `libclang`'s version check contains paths, which
in turn may contain strings that look like version numbers [1][2]:

    .../6.1.0-dev/.../rust_is_available_bindgen_libclang.h:2:9: warning: clang version 11.1.0  [-W#pragma-messages], err: false

which the script will pick up as the version instead of the latter.

It is also the case that versions may appear after the actual version
(e.g. distribution's version text), which was the reason behind `head` [3]:

    .../rust-is-available-bindgen-libclang.h:2:9: warning: clang version 13.0.0 (Fedora 13.0.0-3.fc35) [-W#pragma-messages], err: false

Thus instead ask for a match after the `clang version` string.

Reported-by: Jordan Isaacs <[email protected]>
Closes: Rust-for-Linux/linux#942 [1]
Reported-by: "Ethan D. Twardy" <[email protected]>
Closes: https://lore.kernel.org/rust-for-linux/[email protected]/ [2]
Reported-by: Tiago Lam <[email protected]>
Closes: Rust-for-Linux/linux#789 [3]
Fixes: 78521f3 ("scripts: add `rust_is_available.sh`")
Reviewed-by: Martin Rodriguez Reboredo <[email protected]>
Reviewed-by: Ethan Twardy <[email protected]>
Tested-by: Ethan Twardy <[email protected]>
Reviewed-by: Nathan Chancellor <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Miguel Ojeda <[email protected]>
Signed-off-by: Sasha Levin <[email protected]>
Signed-off-by: Kamal Mostafa <[email protected]>
Signed-off-by: Stefan Bader <[email protected]>

Author: ojeda

scripts/rust_is_available.sh

@@ -112,7 +112,7 @@ fi
 # of the `libclang` found by the Rust bindings generator is suitable.
 bindgen_libclang_version=$( \
 	echo "$bindgen_libclang_output" \
-		| sed -ne 's/.*clang version \([0-9]\+\.[0-9]\+\.[0-9]\+\).*/\1/p'
+		| sed -nE 's:.*clang version ([0-9]+\.[0-9]+\.[0-9]+).*:\1:p'
 )
 bindgen_libclang_min_version=$($min_tool_version llvm)
 bindgen_libclang_cversion=$(get_canonical_version $bindgen_libclang_version)