Fix "access violation" failures that have appeared in new windows builds by disabling compiler optimization on windows

[Strilanc]

The root cause was a compiler autovectorization bug. Turning off optimizations will hurt performance but at least make the code not totally broken.

Reproduction of the bug in a simpler instance:

#include <cstdint>
#include <iostream>

uint64_t repro() {
    uint32_t targets[6]{0, 27, 0, 0, 27, 0};
    uint64_t t = 6;
    for (size_t k = 0; k < 6; k++) {
        if (targets[k] == 27) {
            t -= 2;
        }
    }
    return t;
}

int main() {
    std::cerr << "t=" << repro() << "\n";
    return 0;
}

Go to godbolt, paste the above code, compile it with the compiler x64 msvc v19.51 VS18.6 and flags /O2 and run it and it will print t=8589934594 instead of t=2.

Fixes #1078