cgen: move closure C code to V code under vlib/builtin/closure/ (#24912)

vlib/builtin/closure/closure_windows.c.v

@@ -0,0 +1,53 @@
+module closure
+
+#include <synchapi.h>
+
+struct ClosureMutex {
+	closure_mtx C.SRWLOCK
+}
+
+@[inline]
+fn closure_alloc_platform() &u8 {
+	p := &u8(C.VirtualAlloc(0, g_closure.v_page_size * 2, C.MEM_COMMIT | C.MEM_RESERVE,
+		C.PAGE_READWRITE))
+	return p
+}
+
+@[inline]
+fn closure_memory_protect_platform(ptr voidptr, size isize, attr MemoryProtectAtrr) {
+	mut tmp := u32(0)
+	match attr {
+		.read_exec {
+			_ := C.VirtualProtect(ptr, size, C.PAGE_EXECUTE_READ, &tmp)
+		}
+		.read_write {
+			_ := C.VirtualProtect(ptr, size, C.PAGE_READWRITE, &tmp)
+		}
+	}
+}
+
+@[inline]
+fn get_page_size_platform() int {
+	// Determine system page size
+	mut si := C.SYSTEM_INFO{}
+	C.GetNativeSystemInfo(&si)
+
+	// Calculate required allocation size
+	page_size := int(si.dwPageSize) * (((assumed_page_size - 1) / int(si.dwPageSize)) + 1)
+	return page_size
+}
+
+@[inline]
+fn closure_mtx_lock_init_platform() {
+	C.InitializeSRWLock(&g_closure.closure_mtx)
+}
+
+@[inline]
+fn closure_mtx_lock_platform() {
+	C.AcquireSRWLockExclusive(&g_closure.closure_mtx)
+}
+
+@[inline]
+fn closure_mtx_unlock_platform() {
+	C.ReleaseSRWLockExclusive(&g_closure.closure_mtx)
+}