build: Generate package-config file

Change-Id: Ib776dad5936f1542fd2855a67954f2959c23ef45
Signed-off-by: Patrick Williams <patrick@stwcx.xyz>
diff --git a/Makefile.am b/Makefile.am
index 7ac8318..354cfc9 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -10,6 +10,9 @@
 BUILT_SOURCES = libphosphor_dbus.cpp
 CLEANFILES = libphosphor_dbus.cpp
 
+pkgconfiglibdir = ${libdir}/pkgconfig
+pkgconfiglib_DATA = phosphor-dbus-interfaces.pc
+
 clean-local: clean-dbus
 
 -include Makefile.interfaces