[gwp_asan] Add missing <algorithm> include

After https://reviews.llvm.org/D119667, <algorithm> is no longer
transitively included from various headers. This patch adds the
<algorithm> include into gwp_asan.

Differential Revision: https://reviews.llvm.org/D120172

Author: gulfemsavrun

compiler-rt/lib/gwp_asan/tests/iterate.cpp

@@ -8,6 +8,7 @@
 
 #include "gwp_asan/tests/harness.h"
 
+#include <algorithm>
 #include <set>
 #include <vector>