sw:vec_iree: update doc

Update doc by replacing depreciated cmake variable name IREE_HOST_BINARY_ROOT by IREE_HOST_BIN_DIR.

Change-Id: Ic2b929384badeaa0dd84b77e3d4066090c32a653

README.md

diff --git a/README.md b/README.md
index cc6bc6b..6fe084f 100644
--- a/README.md
+++ b/README.md
@@ -40,7 +40,7 @@
   cmake -B <output dir> -G Ninja \
      -DCMAKE_TOOLCHAIN_FILE="$(realpath sw/vec_iree/cmake/riscv_iree.cmake)" \
      -DCMAKE_BUILD_TYPE=MinSizeRel \
-     -DIREE_HOST_BINARY_ROOT="$(IREE_COMPILER_DIR)/install" \
+     -DIREE_HOST_BIN_DIR="$(IREE_COMPILER_DIR)/install/bin" \
      -DRISCV_TOOLCHAIN_ROOT=$(TOOLCHAINRV32_PATH) \
      <dir>/sw/vec_iree
   cmake --build <output dir> --target all