Upgrade versions of vendored libs

vendor/github.com/DataDog/zstd/zstd_deps.h

@@ -25,6 +25,18 @@
 #ifndef ZSTD_DEPS_COMMON
 #define ZSTD_DEPS_COMMON
 
+/* Even though we use qsort_r only for the dictionary builder, the macro
+ * _GNU_SOURCE has to be declared *before* the inclusion of any standard
+ * header and the script 'combine.sh' combines the whole zstd source code
+ * in a single file.
+ */
+#if defined(__linux) || defined(__linux__) || defined(linux) || defined(__gnu_linux__) || \
+    defined(__CYGWIN__) || defined(__MSYS__)
+#if !defined(_GNU_SOURCE) && !defined(__ANDROID__) /* NDK doesn't ship qsort_r(). */
+#define _GNU_SOURCE
+#endif
+#endif
+
 #include <limits.h>
 #include <stddef.h>
 #include <string.h>