build: handle usrmerge

When building for merged-usr systems, the location of libdir might
be in `/usr/lib`.  We should rely on the passed in `${libdir}` for
installation rather than hard-coding as `/lib/security`

Signed-off-by: Patrick Williams <patrick@stwcx.xyz>
Change-Id: If53ea402f1e50416bc8a0e561d42080ea68742f9
diff --git a/Makefile.am b/Makefile.am
index 165097b..9484da5 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -16,7 +16,7 @@
 	chmod 0600 $(DESTDIR)$(sysconfdir)/key_file
 	chmod 0600 $(DESTDIR)$(sysconfdir)/ipmi_pass
 
-securelibdir = /lib/security
+securelibdir = ${libdir}/security
 securelib_LTLIBRARIES = pam_ipmicheck.la pam_ipmisave.la
 
 pam_ipmicheck_la_SOURCES = src/pam_ipmicheck/pam_ipmicheck.c