Trim trailing '/release/..' when setting _OBJDIR so arm64/aarch64

boot1.efifat is properly located when creating virtual machine images.

Sponsored by:	The FreeBSD Foundation

release/tools/vmimage.subr

@@ -15,6 +15,7 @@ write_partition_layout() {
 	fi
 
 	_OBJDIR="$(make -C ${WORLDDIR} -V .OBJDIR)"
+	_OBJDIR="$(realpath ${_OBJDIR})"
 	if [ -d "${_OBJDIR%%/usr/src}/${TARGET}.${TARGET_ARCH}" ]; then
 		BOOTFILES="/${_OBJDIR%%/usr/src}/${TARGET}.${TARGET_ARCH}/usr/src/sys/boot"
 	else