util: Add an implementation of qsort_r for non-GNU platforms

Android and MSVC don't have qsort_r() so let's provide a util wrapper
that uses the old qsort and thread-local storage.  We use C++ for this
because thread_local is built into C++11 and we can't rely on C11
everywhere.

Acked-by: Erik Faye-Lund <erik.faye-lund@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/10989>

src/util/u_qsort.cpp

@@ -0,0 +1,44 @@
+/*
+ * Copyright © 2020 Intel Corporation
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice (including the next
+ * paragraph) shall be included in all copies or substantial portions of the
+ * Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
+ * IN THE SOFTWARE.
+ */
+
+#include "u_qsort.h"
+#include <thread>
+
+thread_local int (*tl_qsort_r_compar)(const void *, const void *, void *);
+thread_local void *tl_qsort_r_arg;
+
+static int
+qsort_r_compar(const void *a, const void *b)
+{
+   return tl_qsort_r_compar(a, b, tl_qsort_r_arg);
+}
+
+void
+util_tls_qsort_r(void *base, size_t nmemb, size_t size,
+                 int (*compar)(const void *, const void *, void *),
+                 void *arg)
+{
+   tl_qsort_r_compar = compar;
+   tl_qsort_r_arg = arg;
+   return qsort(base, nmemb, size, qsort_r_compar);
+}