refactor: drop Windows host support

crafter-build is moving to a single Flatpak distribution, and there is
no Windows host in that picture: no build.cmd, no MSVC or mingw host
build, no DLL plus launcher. Delete every host-Windows path instead of
leaving it to rot unverified: the cmd.exe command runner and quoting,
the LOCALAPPDATA cache, the MSVC and mingw-host LoadProject variants
with their LIBCXX_DIR and CRAFTER_MINGW_DIR plumbing, the winsock port
probe, the LoadLibrary libclang loader, the console-width and isatty
shims, and the preprocessor guards around the Linux bodies.

The x86_64-w64-mingw32 cross-compile target stays. It is target logic
(output names, -femulated-tls, the libstdc++ link extras, copying a
dependency DLL next to a mingw exe, wine as the runner) and did not
depend on any of the removed code. The msvc target goes with the host
that was the only thing able to use it.

Three target-path warts fixed on the way: ExpectedOutput named a mingw
static library <name>.lib while the archive step wrote lib<name>.a, so
those libraries relinked on every run; the import lib is no longer
copied next to a mingw exe, since the dependency's own bin dir is
already on the link line; and llvm-ar now writes every archive, not
only the LTO ones, so Debug and Release archives are made the same way.

CRAFTER_API and Crafter.Build-Api.h existed only for the DLL boundary.
Nothing downstream used them, so they are removed rather than kept as
an empty macro nobody can verify.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

tests/CompilerWarning/main.cpp

@@ -71,11 +71,7 @@ namespace {
         app.dependencies = { lib };
         // The link step reads a command's output the same way a compile does,
         // so cover it too: an unknown -z value makes ld.lld warn and exit 0.
-        // GNU-style only — lld-link spells its options differently — so the
-        // link case rides along on hosts that use it and is skipped elsewhere.
-        if (!app.target.contains("windows")) {
-            app.linkFlags = { "-Wl,-z,crafter-build-nonexistent-z-value" };
-        }
+        app.linkFlags = { "-Wl,-z,crafter-build-nonexistent-z-value" };
         return app;
     }
 

tests/TestRunnerSpec/main.cpp

@@ -6,9 +6,7 @@ import Crafter.Build;
 using namespace Crafter;
 
 // POSIX env helpers — libc++ exports only std::getenv via `import std`, so
-// forward-declare the setters we need against the C library directly. The
-// test only runs on POSIX hosts (the project.cpp gates new tests by
-// x86_64-pc-linux-gnu) so we don't need a Windows alternative here.
+// forward-declare the setters we need against the C library directly.
 extern "C" int setenv(const char* name, const char* value, int overwrite);
 extern "C" int unsetenv(const char* name);
 
@@ -87,13 +85,11 @@ int main() {
         Check(r.exec.find("QEMU_LD_PREFIX=/opt/alarm-sysroot") != std::string::npos, "ForTarget propagates sysroot to QEMU_LD_PREFIX");
     }
     {
-        // From a Linux host the only sensible way to run x86_64-w64-mingw32 is wine.
+        // The only way to run x86_64-w64-mingw32 output is wine.
         Configuration cfg;
         cfg.target = "x86_64-w64-mingw32";
         TestRunner r = TestRunner::ForTarget(cfg);
-        if (HostTarget().find("linux") != std::string::npos) {
-            Check(r.name == "wine", "ForTarget(mingw) on Linux host uses wine");
-        }
+        Check(r.name == "wine", "ForTarget(mingw) uses wine");
     }
 
     // FromEnv: when the env var is set, it wins over the fallback.