Compile MSAN/TSAN failing test with -O1

This attempts to fix flakes on the bots where the modified test
times out while running under sanitizers.

Turning on the optimizer for just this test appears to mostly fix
the issue.

Author: EricWF

libcxx/test/std/containers/sequences/deque/deque.modifiers/insert_iter_iter.pass.cpp

@@ -9,6 +9,9 @@
 // REQUIRES: long_tests
 // UNSUPPORTED: GCC-ALWAYS_INLINE-FIXME
 
+// This test chokes on the sanitizers during CI runs. It appears we can address most of this by simply enabling optimizations.
+// ADDITIONAL_COMPILE_FLAGS: -O1
+
 // <deque>
 
 // template <class InputIterator>

libcxx/test/std/numerics/rand/rand.dist/rand.dist.bern/rand.dist.bern.negbin/eval.pass.cpp

@@ -8,6 +8,9 @@
 //
 // REQUIRES: long_tests
 
+// This test chokes on the sanitizers during CI runs. It appears we can address most of this by simply enabling optimizations.
+// ADDITIONAL_COMPILE_FLAGS: -O1
+
 // <random>
 
 // template<class IntType = int>