bootchart: fix default init path

Commit 6e1bf7ab99 used the wrong directory; we need rootlibexecdir, not
rootlibdir, as the latter is something like /lib/x86_64-linux-gnu/ on
multi-arch systems.

https://launchpad.net/bugs/1423867

Makefile.am

@@ -199,6 +199,7 @@ AM_CPPFLAGS = \
 	-DKEXEC=\"$(KEXEC)\" \
 	-DLIBDIR=\"$(libdir)\" \
 	-DROOTLIBDIR=\"$(rootlibdir)\" \
+	-DROOTLIBEXECDIR=\"$(rootlibexecdir)\" \
 	-DTEST_DIR=\"$(abs_top_srcdir)/test\" \
 	-I $(top_srcdir)/src \
 	-I $(top_builddir)/src/shared \

src/bootchart/bootchart.c

@@ -73,7 +73,7 @@ int sysfd=-1;
 #define DEFAULT_HZ 25.0
 #define DEFAULT_SCALE_X 100.0 /* 100px = 1sec */
 #define DEFAULT_SCALE_Y 20.0  /* 16px = 1 process bar */
-#define DEFAULT_INIT ROOTLIBDIR "/systemd/systemd"
+#define DEFAULT_INIT ROOTLIBEXECDIR "/systemd"
 #define DEFAULT_OUTPUT "/run/log"
 
 /* graph defaults */