loader: Use the Mach thread port as thread id on Mac OS.
diff --git a/configure.ac b/configure.ac
index 4dd936b..d56250f 100644
--- a/configure.ac
+++ b/configure.ac
@@ -197,6 +197,7 @@
 	linux/param.h \
 	linux/serial.h \
 	linux/ucdrom.h \
+	mach/mach.h \
 	mach/machine.h \
 	machine/cpu.h \
 	machine/limits.h \