Auto-detect btrfs headers to fix build on systems without btrfs-progs-devel (#65)

Add hack/btrfs_installed_tag.sh (same pattern as Podman/Buildah) that
probes for btrfs/ioctl.h and emits exclude_graphdriver_btrfs when the
headers are missing. Wire it into the Makefile via BUILDTAGS so
`make build-bink` works out of the box on any system.

Signed-off-by: HarshwardhanPatil07 <harshpat@redhat.com>

Author: HarshwardhanPatil07

Makefile

@@ -21,6 +21,10 @@ LDFLAGS := -X $(VERSION_PKG).Version=$(VERSION) \
            -X $(VERSION_PKG).GitCommit=$(GIT_COMMIT) \
            -X $(VERSION_PKG).BuildDate=$(BUILD_DATE)
 
+# Build tags (auto-detect optional C dependencies)
+BUILDTAGS ?= \
+	$(shell hack/btrfs_installed_tag.sh)
+
 # Directories
 VM_DIR := containerfiles/cluster-image
 
@@ -29,7 +33,7 @@ all: build-bink
 # Build the bink CLI binary
 build-bink:
 	@echo "=== Building bink CLI binary ==="
-	go build -ldflags "$(LDFLAGS)" -o $(BINK_BINARY) ./cmd/bink
+	go build -tags "$(BUILDTAGS)" -ldflags "$(LDFLAGS)" -o $(BINK_BINARY) ./cmd/bink
 	@echo "✅ bink binary built: $(BINK_BINARY)"
 
 

hack/btrfs_installed_tag.sh

@@ -0,0 +1,7 @@
+#!/usr/bin/env bash
+${CPP:-${CC:-cc} -E} ${CPPFLAGS} - > /dev/null 2> /dev/null << EOF
+#include <btrfs/ioctl.h>
+EOF
+if test $? -ne 0; then
+    echo exclude_graphdriver_btrfs
+fi