add riscv64 build script

Change-Id: I9a1d0569f3c37884ad0d18a715eae01d421ca9fd

Author: alex-spacemit

scripts/build-riscv64-spacemit.sh

@@ -0,0 +1,17 @@
+#!/bin/bash
+
+set -e
+
+SCRIPTS_DIR=$(cd "$(dirname "$(readlink -f "$0")")" && pwd)
+
+cmake -B build-riscv64-spacemit \
+    -DCMAKE_BUILD_TYPE=Release \
+    -DGGML_CPU_RISCV64_SPACEMIT=ON \
+    -DCMAKE_TOOLCHAIN_FILE=${SCRIPTS_DIR}/../cmake/riscv64-spacemit-linux-gnu-gcc.cmake \
+    -DCMAKE_INSTALL_PREFIX=build-riscv64-spacemit/installed
+
+cmake --build build-riscv64-spacemit --parallel 10 --config Release
+
+pushd build-riscv64-spacemit
+make install
+popd