kbuild: rust_is_available: normalize version matching

In order to match the version string, `sed` is used in a couple
cases, and `grep` and `head` in a couple others.

Make the script more consistent and easier to understand by
using the same method, `sed`, for all of them.

This makes the version matching also a bit more strict for
the changed cases, since the strings `rustc ` and `bindgen `
will now be required, which should be fine since `rustc`
complains if one attempts to call it with another program
name, and `bindgen` uses a hardcoded string.

In addition, clarify why one of the existing `sed` commands
does not provide an address like the others.

Reviewed-by: Nathan Chancellor <nathan@kernel.org>
Reviewed-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Martin Rodriguez Reboredo <yakoyoku@gmail.com>
Link: https://lore.kernel.org/r/20230616001631.463536-9-ojeda@kernel.org
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>

Author: ojeda

scripts/rust_is_available.sh

@@ -83,8 +83,7 @@ fi
 # Non-stable and distributions' versions may have a version suffix, e.g. `-dev`.
 rust_compiler_version=$( \
 	LC_ALL=C "$RUSTC" --version 2>/dev/null \
-		| head -n 1 \
-		| grep -oE '[0-9]+\.[0-9]+\.[0-9]+' \
+		| sed -nE '1s:.*rustc ([0-9]+\.[0-9]+\.[0-9]+).*:\1:p'
 )
 rust_compiler_min_version=$($min_tool_version rustc)
 rust_compiler_cversion=$(get_canonical_version $rust_compiler_version)
@@ -111,8 +110,7 @@ fi
 # Non-stable and distributions' versions may have a version suffix, e.g. `-dev`.
 rust_bindings_generator_version=$( \
 	LC_ALL=C "$BINDGEN" --version 2>/dev/null \
-		| head -n 1 \
-		| grep -oE '[0-9]+\.[0-9]+\.[0-9]+' \
+		| sed -nE '1s:.*bindgen ([0-9]+\.[0-9]+\.[0-9]+).*:\1:p'
 )
 rust_bindings_generator_min_version=$($min_tool_version bindgen)
 rust_bindings_generator_cversion=$(get_canonical_version $rust_bindings_generator_version)
@@ -155,6 +153,9 @@ fi
 
 # `bindgen` returned successfully, thus use the output to check that the version
 # of the `libclang` found by the Rust bindings generator is suitable.
+#
+# Unlike other version checks, note that this one does not necessarily appear
+# in the first line of the output, thus no `sed` address is provided.
 bindgen_libclang_version=$( \
 	echo "$bindgen_libclang_output" \
 		| sed -nE 's:.*clang version ([0-9]+\.[0-9]+\.[0-9]+).*:\1:p'