build: add support for fixing up library soname

This makes it possible to declare a package ABI_VERSION independent from the
upstream soname by setting PKG_ABI_VERSION in the package makefile.
The library filename is fixed up for files installed to packages and to the
staging dir. References to the original from executables within the same
package are also fixed up

Signed-off-by: Felix Fietkau <nbd@nbd.name>

scripts/set-abi-version.sh

@@ -0,0 +1,73 @@
+#!/usr/bin/env bash
+# 
+# Copyright (C) 2020 OpenWrt.org
+#
+# This is free software, licensed under the GNU General Public License v2.
+# See /LICENSE for more information.
+#
+SELF=${0##*/}
+
+[ -n "$PATCHELF" ] || {
+  echo "$SELF: patchelf command not defined (PATCHELF variable not set)"
+  exit 1
+}
+
+ABI_VER="$1"
+PATCH_DIR="$2"
+REF_LIST="$3"
+
+[ -n "$ABI_VER" -a -n "$PATCH_DIR" ] || {
+	echo "$SELF: no ABI version or files/directories specified"
+	echo "usage: $SELF <VERSION> [<PATH>...]"
+	exit 1
+}
+
+cmd() {
+	echo "$@" >&2
+	"$@" || exit 1
+}
+
+gen_lib_list() {
+	while read F; do
+		F="${F##*/}"
+		case "$F" in
+			lib*.so*);;
+			*) continue;;
+		esac
+		echo -n "$F:"
+	done < "$REF_LIST"
+}
+
+find "$PATCH_DIR" -type f -a -name 'lib*.so*' | \
+(
+	while read F; do
+		NEW_F="${F%%.so*}.so.$ABI_VER"
+		NEW_NAME="${NEW_F##*/}"
+		[ "$NEW_F" != "$F" ] || continue
+		cmd mv "$F" "$NEW_F"
+		[ "$REF_LIST" ] || cmd ln -s "$NEW_NAME" "$F"
+		cmd $PATCHELF --set-soname "$NEW_NAME" "$NEW_F"
+	done
+)
+
+[ -n "$REF_LIST" ] || exit 0
+
+LIBS="$(gen_lib_list)"
+LIBS="${LIBS%%:}"
+find "$PATCH_DIR" -type f -a -exec file {} \; | \
+  sed -n -e 's/^\(.*\):.*ELF.*\(executable\|relocatable\|shared object\).*,.*/\1:\2/p' | \
+(
+	IFS=":"
+	while read F S; do
+		$PATCHELF --print-needed "$F" | while read L; do
+			BASE_L="${L%%.so*}"
+			for lib in $LIBS; do
+				base_lib="${lib%%.so*}"
+				[ "$BASE_L" = "$base_lib" ] || continue
+				[ "$l" = "$lib" ] && continue
+				cmd $PATCHELF --replace-needed "$L" "$lib" "$F"
+			done
+		done
+	done
+	true
+)