[Msan] Fix the readv and preadv unit tests to pass on FreeBSD

[kutuzov.viktor.84]

Summary

FreeBSD's FILE_TO_READ is large enough to fill up both the buffers. The #include is to declare readv() on FreeBSD.

[kutuzov.viktor.84]

Updated to cover the preadv test.

[eugenis]

LGTM

lib/msan/tests/msan_test.cc

 #if !defined(__FreeBSD__)
 # include <malloc.h>
 # include <sys/sysinfo.h>
 # include <sys/vfs.h>
 # include <mntent.h>
 # include <netinet/ether.h>
 #else
 # include <netinet/in.h>
+# include <sys/uio.h>
 #endif
 
 #if defined(__i386__) || defined(__x86_64__)
 # include <emmintrin.h>
 # define MSAN_HAS_M128 1
 #else
 # define MSAN_HAS_M128 0
 #endif
TEST(MemorySanitizer, readv) {
   iov[0].iov_base = buf + 1;
   iov[0].iov_len = 5;
   iov[1].iov_base = buf + 10;
   iov[1].iov_len = 2000;
   int fd = open(FILE_TO_READ, O_RDONLY);
   ASSERT_GT(fd, 0);
   int sz = readv(fd, iov, 2);
   ASSERT_GE(sz, 0);
-  ASSERT_LT(sz, 5 + 2000);
+  ASSERT_LE(sz, 5 + 2000);
   ASSERT_GT((size_t)sz, iov[0].iov_len);
   EXPECT_POISONED(buf[0]);
   EXPECT_NOT_POISONED(buf[1]);
   EXPECT_NOT_POISONED(buf[5]);
   EXPECT_POISONED(buf[6]);
   EXPECT_POISONED(buf[9]);
   EXPECT_NOT_POISONED(buf[10]);
   EXPECT_NOT_POISONED(buf[10 + (sz - 1) - 5]);