Fix typo in csky-unknown-linux-gnuabiv2.md

Author: taiki-e

src/doc/rustc/src/platform-support/csky-unknown-linux-gnuabiv2.md

@@ -80,7 +80,7 @@ cd hello_world
 ```sh
 CARGO_TARGET_CSKY_UNKNOWN_LINUX_GNUABIV2_RUNNER=${QEMU_PATH}/bin/qemu-cskyv2 -L ${TOOLCHAIN_PATH}/csky-linux-gnuabiv2/libc \
 CARGO_TARGET_CSKY_UNKNOWN_LINUX_GNUABIV2_LINKER=${TOOLCHAIN_PATH}/bin/csky-linux-gnuabiv2-gcc \
-RUSTFLAGS="-C target-features=+crt-static" \
+RUSTFLAGS="-C target-feature=+crt-static" \
 cargo +stage2 run --target csky-unknown-linux-gnuabiv2
 ```