Disable BuildKit to fix docker build on older kernels (#76)

golang:1.24 Debian base introduced a filesystem path that BuildKit's
cache-key walker cannot handle on older kernel versions. Disabling
BuildKit falls back to the classic builder which avoids this issue.

Co-authored-by: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: assaf758

Makefile

@@ -25,7 +25,7 @@ DEB_PATH = iguazio_deb
 
 .PHONY: build
 build:
-	docker build --progress=plain --tag flex-fuse:unstable .
+	DOCKER_BUILDKIT=0 docker build --progress=plain --tag flex-fuse:unstable .
 
 .PHONY: download
 download: