Make ipmi whitelist optional

Not all users of ipmid want to use the whitelist. Or they want to have
their own that behaves differently. This change makes it so one can
disable the built-in whitelist so that OEMs can substitute their own
custom filtering or use none at all.

To disable the whitelist, pass --disable-ipmi-whitelist to configure.
This can be done in Yocto via a bbappend for phosphor-ipmi-host:

EXTRA_OECONF_append = " --disable-ipmi-whitelist"

Tested: Built with and without the whitelist enabled to ensure that the
        whitelist is present when expected to be.

Change-Id: I63f317b6c29ca73cc3296bb2fe38f836004ec35d
Signed-off-by: Vernon Mauery <vernon.mauery@linux.intel.com>
diff --git a/Makefile.am b/Makefile.am
index 02583fe..82fdd5d 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -14,6 +14,12 @@
 providersdir = ${libdir}/ipmid-providers
 providers_LTLIBRARIES =
 
+if FEATURE_IPMI_WHITELIST
+IPMI_WHITELIST_SOURCE = ipmiwhitelist.cpp
+else
+IPMI_WHITELIST_SOURCE =
+endif
+
 bin_PROGRAMS = \
 	ipmid
 
@@ -28,7 +34,7 @@
 	fru-read-gen.cpp
 
 BUILT_SOURCES = \
-	ipmiwhitelist.cpp \
+	$(IPMI_WHITELIST_SOURCE) \
 	$(libipmi20_BUILT_LIST)
 
 CLEANFILES = $(BUILT_SOURCES)
@@ -158,6 +164,7 @@
 	-version-info 0:0:0 -shared
 libsysintfcmds_la_CXXFLAGS = $(COMMON_CXX)
 
+if FEATURE_IPMI_WHITELIST
 libwhitelistdir = ${libdir}/ipmid-providers
 libwhitelist_LTLIBRARIES = libwhitelist.la
 libwhitelist_la_SOURCES = \
@@ -170,6 +177,7 @@
 	-version-info 0:0:0 -shared
 libwhitelist_la_CXXFLAGS = $(COMMON_CXX)
 nodist_libwhitelist_la_SOURCES = ipmiwhitelist.cpp
+endif
 
 nobase_include_HEADERS = \
 	user_channel/channel_layer.hpp \