The mechanics of suppressing debugger trapping and Windows Error Reporting for the crashed child process in a death test are currently guarded under the `GTEST_HAS_SEH` macro. This seems unnecessary, as the logic does not call any APIs related to Structured Error Handling.
Replace the guarding macro with the more permissive `GTEST_OS_WINDOWS`, so that Windows toolchains without SEH support (e.g. MinGW) can benefit from it.
Fixes: #1116
