[Msan] Disable fcvt unit tests on FreeBSD

[emaste]

LGTM

Although fcvt is deprecated and perhaps not found on other platforms, so maybe its better to use #if defined(__GLIBC__) instead.

[eugenis]

LGTM

lib/msan/tests/msan_test.cc

else
       munmap(p2, size);
   }
   if (p1 == p2) {
     EXPECT_NOT_POISONED(*(char*)p2);
     munmap(p2, size);
   }
 }
 
+// There's no fcvt() on FreeBSD.
+#if !defined(__FreeBSD__)
 // FIXME: enable and add ecvt.
 // FIXME: check why msandr does nt handle fcvt.
 TEST(MemorySanitizer, fcvt) {
   int a, b;
   break_optimization(&a);
   break_optimization(&b);
   EXPECT_POISONED(a);
   EXPECT_POISONED(b);
   char *str = fcvt(12345.6789, 10, &a, &b);
   EXPECT_NOT_POISONED(a);
   EXPECT_NOT_POISONED(b);
   ASSERT_NE(nullptr, str);
   EXPECT_NOT_POISONED(str[0]);
   ASSERT_NE(0U, strlen(str));
 }
+#endif
 
+// There's no fcvt_long() on FreeBSD.
+#if !defined(__FreeBSD__)
 TEST(MemorySanitizer, fcvt_long) {
   int a, b;
   break_optimization(&a);
   break_optimization(&b);
   EXPECT_POISONED(a);
   EXPECT_POISONED(b);
   char *str = fcvt(111111112345.6789, 10, &a, &b);
   EXPECT_NOT_POISONED(a);
   EXPECT_NOT_POISONED(b);
   ASSERT_NE(nullptr, str);
   EXPECT_NOT_POISONED(str[0]);
   ASSERT_NE(0U, strlen(str));
 }
-
+#endif
 
 TEST(MemorySanitizer, memchr) {
   char x[10];
   break_optimization(x);
   EXPECT_POISONED(x[0]);
   x[2] = '2';
   void *res;
   EXPECT_UMR(res = memchr(x, '2', 10));