pw_minimal_cpp_stdlib: Fix array alignment in test

Resolves static analyzer complaint by explicitly aligning placement new
target with size of target value.

Change-Id: I7eeed048185bb3886138b760f5f888cd39fa6c46
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/31680
Reviewed-by: Keir Mierle <keir@google.com>
Commit-Queue: Prashanth Swaminathan <prashanthsw@google.com>
diff --git a/pw_minimal_cpp_stdlib/isolated_test.cc b/pw_minimal_cpp_stdlib/isolated_test.cc
index 4f90a82..1be9662 100644
--- a/pw_minimal_cpp_stdlib/isolated_test.cc
+++ b/pw_minimal_cpp_stdlib/isolated_test.cc
@@ -252,7 +252,7 @@
 }
 
 TEST(New, PlacementNew) {
-  unsigned char value[4];
+  alignas(sizeof(int)) unsigned char value[sizeof(int)];
   new (value) int(1234);
 
   int int_value;