docs: improve .gitignore and fix toolchain README path

- Add ignore patterns for toolchain build artifacts
- Fix incorrect path in toolchain README documentation

Signed-off-by: Jiajie Zhou <2293611667@qq.com>

.gitignore

@@ -1,5 +1,13 @@
 # Build files
 build/
+toolchain/arm-linux-eabi_for_x86_64-pc-linux-gnu
+toolchain/riscv64-unkwown-elf_for_x86_64-pc-linux-gnu
+toolchain/binutils-*
+toolchain/gcc-*
+toolchain/gmp-*
+toolchain/mpc-*
+toolchain/mpfr-*
+toolchain/log
 
 # MacOS Cache
 .DS_Store

toolchain/README.md

@@ -24,7 +24,7 @@
 2. **解决网络问题（国内用户推荐，可选）**
 
    ```
-   cd mlibc/toolchain/docker  # 进入工具链的docker配置目录
+   cd mlibc/toolchain  # 进入工具链配置目录
    sudo cp daemon.json /etc/docker/
    sudo systemctl restart docker
    ```