Add Windows fixes so abc compiles natively with GCC.

[cr1901]

This PR fixes some Windows compilation issues I found when compiling with GCC on Windows (MinGW64/MSYS2 specifically in my case):

• Turns some WIN32 checks into more-accurate MSVC-specific checks using _MSC_VER variable. These should not affect compilation with MSVC.
• Remove -lrt from the linked libraries (doesn't really exist for Windows, AFAIR), and add the -lshlwapi library because abc uses PathMatchSpecA somehow.
• ABC's link command-line has unfortunately gotten large enough that it exceeds the 32768-or-so character limit on the command-line. The workaround is Response Files- i.e. supply the command-line arguments via a dynamically-generated file. I use GNU Make's file function for this; the docs even state that response files are an intended usage :D.
• At least in the case of MinGW, uname -s isn't necessarily static (it appends a version string, which can vary between systems). I bring in code from yosys to make the OS variable remain the same between systems.

I mainly follow the yosys branch of ABC, so I was able to compile abc without issue until a recent merge. By looking at the yosys branch and main side-by-side (git log --all --decorate --oneline --graph), it seems all the commits that required me to make these changes were between 68c576c and now (9c41da6).

[wjrforcyber]

I mainly follow the yosys branch of ABC, so I was able to compile abc without issue until a recent merge. By looking at the yosys branch and main side-by-side (git log --all --decorate --oneline --graph), it seems all the commits that required me to make these changes were between 68c576c and now (9c41da6).

Hi, I'm not on windows but have you tried git bisect XXX to locate the exact commit that causes the issue?

[cr1901]

Hi, I'm not on windows but have you tried git bisect XXX to locate the exact commit that causes the issue?

No, I didn't bisect because there isn't a single commit that corresponds to the issues this PR fixes. Additionally, the 32768 character problem is just going to keep coming back, now that the link command is approximately large enough.