win: revert CPU discovery logic to 0.12.3 (#12969)

The behavior change in 0.12.4 is the most likely the root cause of hangs some
users are seeing.  This reverts to the 0.12.3 code, with some added trace
logging.

discover/cpu_windows.go

@@ -5,6 +5,8 @@ import (
 	"log/slog"
 	"syscall"
 	"unsafe"
+
+	"github.com/ollama/ollama/logutil"
 )
 
 type MEMORYSTATUSEX struct {
@@ -99,22 +101,29 @@ func (pkg *winPackage) IsMember(target *GROUP_AFFINITY) bool {
 }
 
 func getLogicalProcessorInformationEx() ([]byte, error) {
-	buf := make([]byte, 1024)
+	buf := make([]byte, 1)
 	bufSize := len(buf)
-	var err error
-	for range 3 {
-		var ret uintptr
-		ret, _, err = GetLogicalProcessorInformationEx.Call(
-			uintptr(RelationAll),
-			uintptr(unsafe.Pointer(&buf[0])),
-			uintptr(unsafe.Pointer(&bufSize)),
-		)
-		if ret == 1 && bufSize <= len(buf) {
-			return buf, nil
-		}
-		buf = make([]byte, bufSize)
+	ret, _, err := GetLogicalProcessorInformationEx.Call(
+		uintptr(RelationAll),
+		uintptr(unsafe.Pointer(&buf[0])),
+		uintptr(unsafe.Pointer(&bufSize)),
+	)
+	if ret != 0 {
+		logutil.Trace("failed to retrieve CPU payload size", "ret", ret, "size", bufSize, "error", err)
+		return nil, fmt.Errorf("failed to determine size info ret:%d %w", ret, err)
+	}
+
+	buf = make([]byte, bufSize)
+	ret, _, err = GetLogicalProcessorInformationEx.Call(
+		uintptr(RelationAll),
+		uintptr(unsafe.Pointer(&buf[0])),
+		uintptr(unsafe.Pointer(&bufSize)),
+	)
+	if ret == 0 {
+		logutil.Trace("failed to retrieve CPU information", "ret", ret, "size", len(buf), "new_size", bufSize, "error", err)
+		return nil, fmt.Errorf("failed to gather processor information ret:%d buflen:%d %w", ret, bufSize, err)
 	}
-	return nil, fmt.Errorf("unable to determine CPU details: %w", err)
+	return buf, nil
 }
 
 func processSystemLogicalProcessorInforationList(buf []byte) []*winPackage {