cmake HAVE_MSAN examples

bitcoin-core/secp256k1 cmake/CheckMemorySanitizer.cmake :6

check_c_source_compiles("
    #if defined(__has_feature)
    #  if __has_feature(memory_sanitizer)
         /* MemorySanitizer is enabled. */
    #  elif
    #    error \"MemorySanitizer is disabled.\"
    #  endif
    #else
    #  error \"__has_feature is not defined.\"
    #endif
  " HAVE_MSAN)

coinbase/cb-mpc vendors/secp256k1/cmake/CheckMemorySanitizer.cmake :6

check_c_source_compiles("
    #if defined(__has_feature)
    #  if __has_feature(memory_sanitizer)
         /* MemorySanitizer is enabled. */
    #  elif
    #    error \"MemorySanitizer is disabled.\"
    #  endif
    #else
    #  error \"__has_feature is not defined.\"
    #endif
  " HAVE_MSAN)