bootchartd: warn if .config looks wrong

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
diff --git a/init/bootchartd.c b/init/bootchartd.c
index 9fd6233..c7388c9 100644
--- a/init/bootchartd.c
+++ b/init/bootchartd.c
@@ -60,6 +60,12 @@
 # endif
 #endif
 
+#if !ENABLE_TAR && !ENABLE_WERROR
+# warning Note: bootchartd requires tar command, but you did not select it.
+#elif !ENABLE_FEATURE_SEAMLESS_GZ && !ENABLE_WERROR
+# warning Note: bootchartd requires tar -z support, but you did not select it.
+#endif
+
 #define BC_VERSION_STR "0.8"
 
 /* For debugging, set to 0: