meta-phosphor: pam-ipmi: prep for usrmerge

Change If53ea402f1e50416bc8a0e561d42080ea68742f9 is going to require
us to pass the `--libdir` configure option so that the install
directory of the PAM modules is not hard-coded, but instead relies on
the `${base_libdir}` derived by the usrmerge feature.  Add this now in
preparation.

This is the same approach taken by the base PAM recipe.

Signed-off-by: Patrick Williams <patrick@stwcx.xyz>
Change-Id: I1a46177f65347521debca54f00145d32872b05b6
diff --git a/meta-phosphor/recipes-extended/pam/pam-ipmi_git.bb b/meta-phosphor/recipes-extended/pam/pam-ipmi_git.bb
index 62d82c9..1eb7154 100644
--- a/meta-phosphor/recipes-extended/pam/pam-ipmi_git.bb
+++ b/meta-phosphor/recipes-extended/pam/pam-ipmi_git.bb
@@ -15,6 +15,8 @@
 
 inherit autotools pkgconfig
 
+EXTRA_OECONF += "--libdir=${base_libdir}"
+
 FILES:${PN} += " \
                ${base_libdir}/security/ \
                ${sysconfdir}/key_file \