Always ignore ldconfig failures

PR #346 [1] has improved ldconfig handling a bit by failing the build
only when ldconfig is invoked as root. However, this causes issues when
building under fakeroot (which sets EUID but does not give permissions).
Furthemore, GNU Makefile conventions [2] expect ldconfig failures to be
simply ignored.

[1]: #346
[2]: https://www.gnu.org/prep/standards/html_node/Utilities-in-Makefiles.html

Makefile

@@ -420,7 +420,7 @@ install_pkgconfig: err all make_install_dirs
 
 install: install_soter_headers install_themis_headers install_static_libs install_shared_libs install_pkgconfig
 ifdef IS_LINUX
-	@ldconfig || (status=$$?; if [ $$(id -u) = "0" ]; then exit $$status; else exit 0; fi)
+	-@ldconfig
 endif
 
 get_version: