[tools][cts] Fix build-cache npm path

npm != node

Change-Id: Ie553bdbc6994bf46be06c3ca9a5ec444716d3ee9
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/158740
Auto-Submit: Ben Clayton <bclayton@google.com>
Reviewed-by: Antonio Maiorano <amaiorano@google.com>
Kokoro: Kokoro <noreply+kokoro@google.com>
Commit-Queue: Antonio Maiorano <amaiorano@google.com>
diff --git a/tools/src/cmd/cts/build_cache/build_cache.go b/tools/src/cmd/cts/build_cache/build_cache.go
index 8f1c0aa..2619b6a 100644
--- a/tools/src/cmd/cts/build_cache/build_cache.go
+++ b/tools/src/cmd/cts/build_cache/build_cache.go
@@ -73,7 +73,7 @@
 }
 
 func (c *cmd) Run(ctx context.Context, cfg common.Config) error {
-	if err := common.InstallCTSDeps(ctx, c.flags.ctsDir, fileutils.NodePath()); err != nil {
+	if err := common.InstallCTSDeps(ctx, c.flags.ctsDir, c.flags.npmPath); err != nil {
 		return err
 	}
 	list, err := common.BuildCache(ctx, c.flags.ctsDir, c.flags.nodePath, c.flags.npmPath, c.flags.authFlags)