toolchain.mk: add clang-toolchains target

Add "make clang-toolchains" to download and extract Clang 9.0.1 into
$(ROOT)/clang-9.0.1.

Usage:
 $ make clang-toolchains

Then use the following command to build OP-TEE and TAs with Clang:
 $ PATH=$PWD/../clang-9.0.1/bin:$PATH make COMPILER=clang

Signed-off-by: Jerome Forissier <jerome@forissier.org>
Reviewed-by: Victor Chong <victor.chong@linaro.org>
Acked-by: Etienne Carriere <etienne.carriere@linaro.org>

get_clang.sh

+#!/bin/bash
+#
+# Download and extract Clang from the GitHub release page.
+# We want a x86_64 cross-compiler capable of generating aarch64 and armv7a code
+# *and* we want the compiler-rt libraries for these architectures
+# (libclang_rt.*.a).
+# Clang is configured to be able to cross-compile to all the supported
+# architectures by default (see <clang path>/bin/llc --version) which is great,
+# but compiler-rt is included only for the host architecture. Therefore we need
+# to combine several packages into one, which is the purpose of this script.
+#
+# Usage: get_clang.sh [path]
+
+DEST=${1:-./clang-9.0.1}
+
+VER=9.0.1
+X86_64=clang+llvm-${VER}-x86_64-linux-gnu-ubuntu-16.04
+AARCH64=clang+llvm-${VER}-aarch64-linux-gnu
+ARMV7A=clang+llvm-${VER}-armv7a-linux-gnueabihf
+
+set -x
+
+TMPDEST=${DEST}_tmp${RANDOM}
+
+if [ -e ${TMPDEST} ]; then
+  echo Error: ${TMPDEST} exists
+  exit 1
+fi
+
+function cleanup() {
+  rm -f ${X86_64}.tar.xz ${AARCH64}.tar.xz ${ARMV7A}.tar.xz
+  rm -rf ${AARCH64} ${ARMV7A}
+}
+
+trap "{ exit 2; }" INT
+trap cleanup EXIT
+
+(wget -nv https://github.com/llvm/llvm-project/releases/download/llvmorg-${VER}/${X86_64}.tar.xz && tar xf ${X86_64}.tar.xz) &
+pids=$!
+(wget -nv https://github.com/llvm/llvm-project/releases/download/llvmorg-${VER}/${AARCH64}.tar.xz && tar xf ${AARCH64}.tar.xz) &
+pids="$pids $!"
+(wget -nv https://github.com/llvm/llvm-project/releases/download/llvmorg-${VER}/${ARMV7A}.tar.xz && tar xf ${ARMV7A}.tar.xz) &
+pids="$pids $!"
+
+wait $pids || exit 1
+
+mv ${X86_64} ${TMPDEST} || exit 1
+cp ${AARCH64}/lib/clang/${VER}/lib/linux/* ${TMPDEST}/lib/clang/${VER}/lib/linux || exit 1
+cp ${ARMV7A}/lib/clang/${VER}/lib/linux/* ${TMPDEST}/lib/clang/${VER}/lib/linux || exit 1
+mv ${TMPDEST} ${DEST}

toolchain.mk

@@ -37,3 +37,18 @@ aarch32:
 .PHONY: aarch64
 aarch64:
 	$(call dltc,$(AARCH64_PATH),$(SRC_AARCH64_GCC),$(AARCH64_GCC_VERSION))
+
+CLANG_PATH			?= $(ROOT)/clang-9.0.1
+
+# Download the Clang compiler with LLVM tools and compiler-rt libraries
+define dl-clang
+	@if [ ! -d "$(1)" ]; then \
+		./get_clang.sh $(1); \
+	else \
+		echo "$(1) already exists"; \
+	fi
+endef
+
+.PHONY: clang-toolchains
+clang-toolchains:
+	$(call dl-clang,$(CLANG_PATH))