Switch windows build to fully dynamic

Refactor where we store build outputs, and support a fully dynamic loading
model on windows so the base executable has no special dependencies thus
doesn't require a special PATH.

llm/shim_ext_server_linux.go

@@ -0,0 +1,46 @@
+package llm
+
+import (
+	"embed"
+	"errors"
+	"fmt"
+	"io/fs"
+	"log"
+	"os"
+	"strings"
+)
+
+//go:embed llama.cpp/gguf/build/*/*/lib/*.so
+var libEmbed embed.FS
+
+func updatePath(dir string) {
+	pathComponents := strings.Split(os.Getenv("PATH"), ":")
+	for _, comp := range pathComponents {
+		if comp == dir {
+			return
+		}
+	}
+	newPath := strings.Join(append(pathComponents, dir), ":")
+	log.Printf("Updating PATH to %s", newPath)
+	os.Setenv("PATH", newPath)
+}
+
+func verifyDriverAccess() error {
+	// Only check ROCm access if we have the dynamic lib loaded
+	if _, rocmPresent := AvailableShims["rocm"]; rocmPresent {
+		// Verify we have permissions - either running as root, or we have group access to the driver
+		fd, err := os.OpenFile("/dev/kfd", os.O_RDWR, 0666)
+		if err != nil {
+			if errors.Is(err, fs.ErrPermission) {
+				return fmt.Errorf("Radeon card detected, but permissions not set up properly.  Either run ollama as root, or add you user account to the render group.")
+			} else if errors.Is(err, fs.ErrNotExist) {
+				// expected behavior without a radeon card
+				return nil
+			}
+
+			return fmt.Errorf("failed to check permission on /dev/kfd: %w", err)
+		}
+		fd.Close()
+	}
+	return nil
+}