patchpkg: fix system CUDA lib search

As part of the auto-patching for CUDA, devbox searches for the system's
libcuda (installed by the driver) and adds it to the Nix store. This
fixes a couple of bugs with that search process:

- When creating the soname links, the base name of the path to libcuda
  wasn't being used. This would lead to creating symlinks like
  "lib/libcuda.so.1", which would fail because a lib subdirectory didn't
  exist.
- Ensure the `src` attribute is set in the patch flake so that devbox
  knows the path the flake source (which contains the copied libcuda) at
  build time.

internal/patchpkg/builder.go

@@ -327,11 +327,15 @@ func (d *DerivationBuilder) findCUDA(ctx context.Context, out *packageFS) error
 		return fmt.Errorf("patch flake didn't set $src to the path to its source tree")
 	}
 
-	glob, err := fs.Glob(d.src, "lib/libcuda.so*")
+	pattern := "lib/libcuda.so*"
+	slog.DebugContext(ctx, "looking for system CUDA libraries in flake", "glob", filepath.Join(d.src.storePath, "lib/libcuda.so*"))
+	glob, err := fs.Glob(d.src, pattern)
 	if err != nil {
 		return fmt.Errorf("glob system libraries: %v", err)
 	}
-	if len(glob) != 0 {
+	if len(glob) == 0 {
+		slog.DebugContext(ctx, "no system CUDA libraries found in flake")
+	} else {
 		err := d.copyDir(out, "lib")
 		if err != nil {
 			return fmt.Errorf("copy system library: %v", err)

internal/patchpkg/elf.go

@@ -182,14 +182,14 @@ func (lib SharedLibrary) CopyAndLink(dir string) error {
 		return err
 	}
 
-	sonameLink := filepath.Join(dir, lib.Soname)
+	sonameLink := filepath.Join(dir, filepath.Base(lib.Soname))
 	var sonameErr error
 	if lib.Soname != "" {
 		// Symlink must be relative.
 		sonameErr = os.Symlink(filepath.Base(lib.RealName), sonameLink)
 	}
 
-	linkerNameLink := filepath.Join(dir, lib.LinkerName)
+	linkerNameLink := filepath.Join(dir, filepath.Base(lib.LinkerName))
 	var linkerNameErr error
 	if lib.LinkerName != "" {
 		// Symlink must be relative.
@@ -209,9 +209,9 @@ func (lib SharedLibrary) CopyAndLink(dir string) error {
 
 func (lib SharedLibrary) LogValue() slog.Value {
 	return slog.GroupValue(
-		slog.String("lib.path", lib.Name()),
-		slog.String("lib.linkername", lib.LinkerName),
-		slog.String("lib.soname", lib.Soname),
-		slog.String("lib.realname", lib.RealName),
+		slog.String("path", lib.Name()),
+		slog.String("linkername", lib.LinkerName),
+		slog.String("soname", lib.Soname),
+		slog.String("realname", lib.RealName),
 	)
 }

internal/shellgen/tmpl/glibc-patch.nix.tmpl

@@ -94,7 +94,7 @@
         gcc = if isLinux then nixpkgs-glibc.legacyPackages."${system}".stdenv.cc.cc.lib else null;
 
         DEVBOX_DEBUG = 1;
-
+	src = self;
         builder = "${devbox.packages.${system}.default}/bin/devbox";
         args = [ "patch" "--restore-refs" ] ++
           (if glibc != null then [ "--glibc" "${glibc}" ] else [ ]) ++