Ensure that the test version of the command line tool is stable for benchmarking (#2076)

Some benchmark suites contain test cases that have nonreproducible
behaviour. This is mostly caused by relying on "now" when dealing
with dates or timestamps, instead of using a fixed moment. (A
notorious example is the crypto-aes.js test case of the sunspider
bechmark suite, where the heap memory consumption can vary between
34K-41K heap because of using `(new Date()).getTime()`.)

This commit renames the jerry-minimal command line tool to
jerry-test (to better reflect its purpose) and adds extra code,
which intercepts some calls to libc (`gettimeofday`, `rand`) and
pins their results to some fixed values. This makes the tool
useless in a general case but ensures stable results when
benchmarking -- for which it is mostly used.

As a side effect, the commit also changes jerry-libc by making all
libc functions weak symbols to allow their override from
application code.

JerryScript-DCO-1.0-Signed-off-by: Akos Kiss akiss@inf.u-szeged.hu

jerry-libc/jerry-libc-printf.c

@@ -469,7 +469,7 @@ libc_printf_write_u_o_x_X (FILE *stream, /**< stream pointer */
  *
  * @return number of characters printed
  */
-int
+int __attr_weak___
 vfprintf (FILE *stream, /**< stream pointer */
           const char *format, /**< format string */
           va_list args) /**< arguments */
@@ -719,7 +719,7 @@ vfprintf (FILE *stream, /**< stream pointer */
  *
  * @return number of characters printed
  */
-int
+int __attr_weak___
 fprintf (FILE *stream, /**< stream pointer */
          const char *format, /**< format string */
          ...) /**< parameters' values */
@@ -740,7 +740,7 @@ fprintf (FILE *stream, /**< stream pointer */
  *
  * @return number of characters printed
  */
-int
+int __attr_weak___
 printf (const char *format, /**< format string */
         ...) /**< parameters' values */
 {