build: use a common library for shared pieces

Signed-off-by: Patrick Venture <venture@google.com>
Change-Id: Ic4b645091c71f270ba3b2f290f7206ebe3222f1d
diff --git a/bmc/Makefile.am b/bmc/Makefile.am
index c46a8cd..be3346c 100644
--- a/bmc/Makefile.am
+++ b/bmc/Makefile.am
@@ -2,10 +2,8 @@
 
 noinst_LTLIBRARIES = libfirmwareblob_common.la
 libfirmwareblob_common_la_SOURCES = \
-	$(top_srcdir)/util.cpp \
 	firmware_handler.cpp \
 	file_handler.cpp \
-	$(top_srcdir)/internal/sys.cpp \
 	prepare_systemd.cpp \
 	verify_systemd.cpp \
 	update_systemd.cpp
@@ -37,6 +35,7 @@
         $(PHOSPHOR_LOGGING_LIBS) \
         $(CODE_COVERAGE_LIBS) \
         -lstdc++fs
+libfirmwareblob_common_la_LIBADD = $(top_builddir)/libfirmware_common.la
 
 libfirmwareblobdir = ${libdir}/ipmid-providers
 libfirmwareblob_LTLIBRARIES = libfirmwareblob.la