runtime_loader: set default alignment to max_align_t if available

...as done by mmlr in malloc_debug.
TLS blocks are expected to be aligned, gcc happily uses SSE instructions,
triggering exceptions.

Change-Id: I5a7bfe287600286e724cd13fe9aa7c7916091979
Reviewed-on: https://review.haiku-os.org/c/haiku/+/3768
Reviewed-by: Adrien Destugues <pulkomandy@gmail.com>

src/system/runtime_loader/heap.cpp

@@ -36,7 +36,12 @@
 	To ease list handling, the list anchor itself is a free chunk with
 	size 0 that can't be allocated.
 */
+#if __cplusplus >= 201103L
+#include <cstddef>
+const static size_t kAlignment = alignof(max_align_t);
+#else
 const static size_t kAlignment = 8;
+#endif
 	// all memory chunks will be a multiple of this
 
 const static size_t kInitialHeapSize = 64 * 1024;