process-debuginfo: Add .gnu_debuglink symlink for vmlinux

`eu-strip --strip-all` started to strip .symtab for un-def kernel
triggering different code path in crash(8) thus making it follow
value of `.gnu_debuglink` section and miss vmlinux.debug.

Also, this seems to be more portable overall - we can find vmlinux by
prepending `/usr/lib/debug` or by appending `.debug`.

With educated guess we assume eu-strip will put "BASENAME.debug" in
`.gnu_debuglink`.

Signed-off-by: Vitaly Chikunov <vt@altlinux.org>

scripts/find-debuginfo-files.in

@@ -34,6 +34,9 @@ while read -r f; do
 		else
 			Warning "Expected $f not found."
 		fi
+		if [ -L ".$f.debug" ] && [ -e ".$f.debug" ]; then
+			printf '%s\n' "$f.debug" >> .tmp/links
+		fi
 	fi
 	fbin=$f # Actual binary for linking
 

scripts/process-debuginfo.in

@@ -20,6 +20,7 @@ rezip=
 elfcompress=
 strip_rel=
 strip_btf='--keep-section=.BTF'
+debuglink=
 
 if [ -z "${f#./lib/modules/*.ko}" ]; then
 	elfcompress=yes
@@ -56,6 +57,7 @@ elif [ -z "${f##./boot/vmlinuz-*}" ]; then
 	if [ -f "$vmlinuxs" ]; then
 		install -pD -m644 "$vmlinuxs" "$vmlinuxd"
 		f=$vmlinuxd
+		debuglink="$vmlinuxd.debug"
 	else
 		Warning "vmlinux not found in $RPM_BUILD_DIR for -debuginfo"
 		exit
@@ -104,6 +106,7 @@ fi
 if [ -n "$strip" ]; then
 	mkdir -p "${debugf%/*}"
 	LD_ORIGIN_PATH=/usr/bin eu-strip $strip $strip_rel $strip_btf --remove-comment -f "$debugf" "$f"
+	[ -z "$debuglink" ] || ln -sr "$debugf" "$debuglink"
 
 	if [ -n "$elfcompress" ] && [ -x /usr/bin/eu-elfcompress ]; then
 		LD_ORIGIN_PATH=/usr/bin eu-elfcompress --quiet "$debugf"