package/llvm: add BPF backend

bcc is a front-end tool for eBPF :
https://github.com/iovisor/bcc/blob/master/README.md.
eBPF is the most powerful Linux tracer, and bcc
allows to write eBPF scripts in C and PYTHON3.

BCC requires enabling LLVM backend BPF support.

Signed-off-by: Jugurtha BELKALEM <jugurtha.belkalem@smile.fr>
Signed-off-by: Romain Naour <romain.naour@gmail.com>
Tested-by: Qais Yousef <qais.yousef@arm.com>
Reviewed-by: Qais Yousef <qais.yousef@arm.com>
Cc: Qais Yousef <qais.yousef@arm.com>
Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>

package/llvm/Config.in

@@ -47,6 +47,12 @@ config BR2_PACKAGE_LLVM_RTTI
 
 	  https://llvm.org/docs/HowToSetUpLLVMStyleRTTI.html
 
+config BR2_PACKAGE_LLVM_BPF
+	bool "BPF backend"
+	help
+	  Build BPF target. Select this option if you are going
+	  to install bcc on the target.
+
 endif
 
 comment "llvm needs a toolchain w/ wchar, threads, C++, gcc >= 4.8, dynamic library"

package/llvm/llvm.mk

@@ -62,6 +62,11 @@ ifeq ($(BR2_PACKAGE_LLVM_AMDGPU),y)
 LLVM_TARGETS_TO_BUILD += AMDGPU
 endif
 
+# Build BPF backend
+ifeq ($(BR2_PACKAGE_LLVM_BPF),y)
+LLVM_TARGETS_TO_BUILD += BPF
+endif
+
 # Use native llvm-tblgen from host-llvm (needed for cross-compilation)
 LLVM_CONF_OPTS += -DLLVM_TABLEGEN=$(HOST_DIR)/bin/llvm-tblgen