llvm-bpf: fix rebuild check for generating tarball

Check the version file, as it will be regenerated on rebuild

Signed-off-by: Felix Fietkau <nbd@nbd.name>

target/llvm-bpf/Makefile

@@ -14,7 +14,7 @@ LLVM_VERSION := $(shell cat $(STAGING_DIR_HOST)/llvm-bpf/.llvm-version)
 LLVM_BPF_PREFIX := llvm-bpf-$(LLVM_VERSION).$(HOST_OS)-$(HOST_ARCH)
 LLVM_TAR := $(BIN_DIR)/$(LLVM_BPF_PREFIX).tar.xz
 
-$(LLVM_TAR): $(HOST_STAMP_INSTALLED)
+$(LLVM_TAR): $(STAGING_DIR_HOST)/llvm-bpf/.llvm-version
 	tar -C $(STAGING_DIR_HOST) \
 		-I '$(STAGING_DIR_HOST)/bin/xz -7e -T$(if $(filter 1,$(NPROC)),2,0)' \
 		$(if $(SOURCE_DATE_EPOCH),--mtime="@$(SOURCE_DATE_EPOCH)") \