llvm-bpf: support creating a tarball in bin

This can be used for adding the toolchain to an existing tree without having
to build it from scratch.
Enable building the toolchain + tarball by default on buildbot

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

target/sdk/Config.in

@@ -7,4 +7,11 @@ config SDK
 	  with a precompiled toolchain. It can be used to develop and
 	  test packages for OpenWrt before including them in the buildroot
 
-
+config SDK_LLVM_BPF
+	bool "Build the LLVM-BPF toolchain tarball"
+	depends on BPF_TOOLCHAIN_BUILD_LLVM
+	default BUILDBOT
+	help
+	  This is a tarball of the precompiled LLVM toolchain suitable
+	  for unpacking into the buildroot/SDK. It is used to build packages
+	  that ship with eBPF kernel modules

target/sdk/Makefile

@@ -34,7 +34,8 @@ EXCLUDE_DIRS:= \
 	*.install.flags \
 	*.install \
 	*/doc \
-	*/share/locale
+	*/share/locale \
+	*/llvm-bpf*
 
 SDK_DIRS = \
 		$(STAGING_SUBDIR_HOST) \