Add musl tool chain for linux arm64

Signed-off-by: Paulo Gomes <paulo.gomes@weave.works>

Author: Paulo Gomes

Makefile

@@ -12,6 +12,7 @@ LIBGIT2_PATH := $(TARGET_DIR)
 LIBGIT2_LIB_PATH := $(LIBGIT2_PATH)/lib
 LIBGIT2_LIB64_PATH := $(LIBGIT2_PATH)/lib64
 LIBGIT2 := $(LIBGIT2_LIB_PATH)/libgit2.a
+MUSL-CC =
 
 export CGO_ENABLED=1
 export LIBRARY_PATH=$(LIBGIT2_LIB_PATH):$(LIBGIT2_LIB64_PATH)
@@ -27,9 +28,11 @@ endif
 
 ifeq ($(shell uname -s),Linux)
 ifneq ($(shell uname -m),x86_64)
-	export CC=$(shell uname -m)-linux-musl-gcc
-	export CXX=$(shell uname -m)-linux-musl-g++
-	export AR=$(shell uname -m)-linux-musl-ar
+	MUSL-PREFIX=$(REPOSITORY_ROOT)/build/musl/aarch64-linux-musl-native/bin/aarch64-linux-musl
+	MUSL-CC=$(MUSL-PREFIX)-gcc
+	export CC=$(MUSL-PREFIX)-gcc
+	export CXX=$(MUSL-PREFIX)-g++
+	export AR=$(MUSL-PREFIX)-ar
 endif
 endif
 
@@ -67,7 +70,10 @@ builder:
 # install qemu emulators
 	docker run -it --rm --privileged tonistiigi/binfmt --install all
 
-$(LIBGIT2):
+$(MUSL-CC):
+	./hack/download-musl.sh
+
+$(LIBGIT2): $(MUSL-CC)
 ifeq ($(shell uname -s),Darwin)
 	TARGET_DIR=$(TARGET_DIR) BUILD_ROOT_DIR=$(BUILD_ROOT_DIR) \
 		./hack/static.sh all

hack/download-musl.sh

@@ -0,0 +1,24 @@
+#!/usr/bin/env bash
+
+MUSL_AARCH64_FILENAME=aarch64-linux-musl-native.tgz
+MUSL_AARCH64_URL="https://more.musl.cc/11.2.1/x86_64-linux-musl/${MUSL_AARCH64_FILENAME}"
+MUSL_AARCH64_SHA512=16d544e09845c9dbba50f29e0cb04dd661e17eb63c56acad6a67fd2a78aa7596b792477c7177d3cd56d408a27dc291a90507df882f2b099c0f25511ce08fd3b5
+
+ROOT_DIR="$(git rev-parse --show-toplevel)"
+MUSL_DIR="${ROOT_DIR}/build/musl"
+
+if [ ! -f "${MUSL_DIR}/bin" ]; then
+    TARGET_FILE="${MUSL_DIR}/${MUSL_AARCH64_FILENAME}"
+    mkdir -p "${MUSL_DIR}"
+
+    echo "${MUSL_AARCH64_SHA512}  ${TARGET_FILE}"
+    curl -o "${TARGET_FILE}" -LO "${MUSL_AARCH64_URL}"
+    if ! echo "${MUSL_AARCH64_SHA512}  ${TARGET_FILE}" | sha512sum --check; then
+        echo "Checksum failed for ${MUSL_AARCH64_FILENAME}."
+        rm -rf "${MUSL_DIR}"
+        exit 1
+    fi
+
+    tar xzf "${TARGET_FILE}" -C "${MUSL_DIR}"
+    rm "${TARGET_FILE}"
+fi