fix gettimeofday() on alpha (see https://bugs.debian.org/890813)

[dkg]

In https://bugs.debian.org/890813, Michael Cree mcree@orcon.net.nz
reports:

The faketime package fails to work correctly on the Alpha
architecture. This failure of faketime to work correctly is the
reason for the mbedtls FTBFS, which uses faketime in its test
suite [1].

Consider the following test program (which I call "time-test"):

#include <stdio.h>
#include <sys/time.h>
#include <unistd.h>

int main(void)
{
struct timeval tv;

 for (int j=0; j<5; j++) {
     usleep(10000);
     gettimeofday(&tv, NULL);
     printf("s=%ld    us=%ld\n", tv.tv_sec, tv.tv_usec);
 }
 return 0;

}

When run it produces output like:

s=1519025990 us=838219
s=1519025990 us=848965
s=1519025990 us=859711
s=1519025990 us=870456
s=1519025990 us=881202

But when run as (with faketime built in its source directory):

LD_PRELOAD=faketime-0.9.7/src/libfaketime.so.1 FAKETIME="-1d" ./time-test

the output is:

s=2199023743604 us=0
s=2199023657204 us=0
s=2199023570804 us=0
s=2199023484404 us=0
s=2199023398004 us=0

which is definitely not correct.

The reason for the incorrect behaviour is that there are two
gettimeofday symbols in libc on Alpha and the dlsym() call to link
to the gettimeofday() is picking up the function with the wrong ABI.
I attach a patch to fix that. Faketime built with the attached
patch works correctly and with a fixed faketime the mbedtls source
package builds to completion on Alpha.