Add vendored RISC-V cross-compiler

.gitignore

@@ -67,12 +67,15 @@
 
 /vendor/cross/build/i386/binutils/*
 !/vendor/cross/build/i386/binutils/.keep
-
 /vendor/cross/build/i386/gcc/*
 !/vendor/cross/build/i386/gcc/.keep
 
+/vendor/cross/build/riscv64/binutils/*
+!/vendor/cross/build/riscv64/binutils/.keep
+/vendor/cross/build/riscv64/gcc/*
+!/vendor/cross/build/riscv64/gcc/.keep
+
 /vendor/cross/build/x86_64/binutils/*
 !/vendor/cross/build/x86_64/binutils/.keep
-
 /vendor/cross/build/x86_64/gcc/*
 !/vendor/cross/build/x86_64/gcc/.keep

vendor/cross/build/riscv64/build.sh

@@ -0,0 +1,21 @@
+#!/bin/sh
+
+set -e
+
+ARCH='riscv64'
+TARGET="$ARCH-elf"
+REPO="$(pwd)"
+PREFIX="$REPO/vendor/cross"
+PATH="$PREFIX/bin:$PATH"
+
+if [ -z "$J" ]; then J='1'; fi
+
+cd "$REPO/vendor/cross/build/$ARCH/binutils"
+../../../../binutils-2.37/configure --target="$TARGET" --prefix="$PREFIX" --with-sysroot --disable-nls --disable-werror
+make -j"$J"
+make install
+
+cd "$REPO/vendor/cross/build/$ARCH/gcc"
+../../../../gcc-11.2.0/configure --target="$TARGET" --prefix="$PREFIX" --disable-nls --enable-languages=c,c++ --without-headers
+make -j"$J" all-gcc all-target-libgcc
+make install-gcc install-target-libgcc