Fix libproc test case to work with clang premature optimization

observed with -O2 (used by default).
Avoid function inlining for t1_bkpt_t on which we set a breakpoint.
Otherwise the address of the function is never called thus the
breakpoint never triggers.

Reported by:	zont
Reviewed by:	rpaulo

lib/libproc/test/t1-bkpt/t1-bkpt.c

@@ -36,7 +36,7 @@
 #include <string.h>
 #include <libproc.h>
 
-int
+int __noinline
 t1_bkpt_t()
 {
 	printf("TEST OK\n");