[Msan] Disable the fgetgrent_r unit test on FreeBSD

[eugenis]

LGTM

compiler-rt/trunk/lib/msan/tests/msan_test.cc

TEST(MemorySanitizer, getgrent_r) {
   ASSERT_EQ(0, res);
   EXPECT_NOT_POISONED(grp.gr_name);
   ASSERT_TRUE(grp.gr_name != NULL);
   EXPECT_NOT_POISONED(grp.gr_name[0]);
   EXPECT_NOT_POISONED(grp.gr_gid);
   EXPECT_NOT_POISONED(grpres);
 }
 
+// There's no fgetgrent_r() on FreeBSD.
+#if !defined(__FreeBSD__)
 TEST(MemorySanitizer, fgetgrent_r) {
   FILE *fp = fopen("/etc/group", "r");
   struct group grp;
   struct group *grpres;
   char buf[10000];
   setgrent();
   int res = fgetgrent_r(fp, &grp, buf, sizeof(buf), &grpres);
   ASSERT_EQ(0, res);
   EXPECT_NOT_POISONED(grp.gr_name);
   ASSERT_TRUE(grp.gr_name != NULL);
   EXPECT_NOT_POISONED(grp.gr_name[0]);
   EXPECT_NOT_POISONED(grp.gr_gid);
   EXPECT_NOT_POISONED(grpres);
   fclose(fp);
 }
+#endif
 
 TEST(MemorySanitizer, getgroups) {
   int n = getgroups(0, 0);
   gid_t *gids = new gid_t[n];
   int res = getgroups(n, gids);
   ASSERT_EQ(n, res);
   for (int i = 0; i < n; ++i)
     EXPECT_NOT_POISONED(gids[i]);