kbuild: Make ld-version.sh more robust against version string changes

After [1] in upstream LLVM, ld.lld's version output became slightly
different when the cmake configuration option LLVM_APPEND_VC_REV is
disabled.

Before:

  Debian LLD 19.0.0 (compatible with GNU linkers)

After:

  Debian LLD 19.0.0, compatible with GNU linkers

This results in ld-version.sh failing with

  scripts/ld-version.sh: 18: arithmetic expression: expecting EOF: "10000 * 19 + 100 * 0 + 0,"

because the trailing comma is included in the patch level part of the
expression. While [1] has been partially reverted in [2] to avoid this
breakage (as it impacts the configuration stage and it is present in all
LTS branches), it would be good to make ld-version.sh more robust
against such miniscule changes like this one.

Use POSIX shell parameter expansion [3] to remove the largest suffix
after just numbers and periods, replacing of the current removal of
everything after a hyphen. ld-version.sh continues to work for a number
of distributions (Arch Linux, Debian, and Fedora) and the kernel.org
toolchains and no longer errors on a version of ld.lld with [1].

Fixes: 02aff85 ("kbuild: check the minimum linker version in Kconfig")
Link: llvm/llvm-project@0f9fbbb [1]
Link: llvm/llvm-project@649cdfc [2]
Link: https://pubs.opengroup.org/onlinepubs/9699919799/utilities/V3_chap02.html [3]
Suggested-by: Fangrui Song <[email protected]>
Reviewed-by: Fangrui Song <[email protected]>
Signed-off-by: Nathan Chancellor <[email protected]>
Reviewed-by: Nicolas Schier <[email protected]>
Signed-off-by: Masahiro Yamada <[email protected]>

Author: nathanchance

scripts/ld-version.sh

@@ -57,9 +57,11 @@ else
 	fi
 fi
 
-# Some distributions append a package release number, as in 2.34-4.fc32
-# Trim the hyphen and any characters that follow.
-version=${version%-*}
+# There may be something after the version, such as a distribution's package
+# release number (like Fedora's "2.34-4.fc32") or punctuation (like LLD briefly
+# added before the "compatible with GNU linkers" string), so remove everything
+# after just numbers and periods.
+version=${version%%[!0-9.]*}
 
 cversion=$(get_canonical_version $version)
 min_cversion=$(get_canonical_version $min_version)