libpaper: Add SOVERSION guard

%ci:no-build

packages/libpaper/build.sh

@@ -12,6 +12,18 @@ TERMUX_PKG_EXTRA_CONFIGURE_ARGS="
 "
 TERMUX_PKG_PROVIDES="paper"
 
+termux_step_post_get_source() {
+	# Do not forget to bump revision of reverse dependencies and rebuild them
+	# after SOVERSION is changed.
+	local _SOVERSION=2
+
+	local v=$(echo ${TERMUX_PKG_VERSION#*:} | cut -d . -f 1)
+	if [ "${v}" != "${_SOVERSION}" ]; then
+		termux_error_exit "SOVERSION guard check failed."
+	fi
+
+}
+
 termux_step_pre_configure() {
 	# 210x297 (in mm) is A4 size. Use as default to be provided by locale.
 	CFLAGS+=" -D_NL_PAPER_WIDTH=210 -D_NL_PAPER_HEIGHT=297"