update README.md

Signed-off-by: Wang Chen <wangchen20@iscas.ac.cn>

README.md

@@ -2,11 +2,12 @@ This repo is just used for building of Chrome(android riscv64), and
 simulate android NDK befoer google releases offiical version that 
 supports riscv64.
 
-Based on android ndk packages from https://ci.android.com/builds/branches/aosp-master-ndk/grid (linux),
-but stripping some other items except the sysroot, due to space limitation from github.
-
-Before usage, make sure to remove the existing `toolchains/llvm/prebuilt/linux-x86_64/sysroot/usr/lib/riscv64-linux-android`,
-which is a symbol link and re-create anther one with the same name and
-point to the `usr/lib/riscv64-linux-android/` of repo
-<https://android.googlesource.com/toolchain/prebuilts/sysroot/platform/riscv64-linux-android>.
+Based on android ndk packages from
+<https://ci.android.com/builds/branches/aosp-master-ndk/grid> (linux),
+but stripping some other items (expecially the clangs) and keep some,
+such as sysroot etc. due to space limitation from github.
 
+Note, following entries are symbol files, you may have to update
+them to correct position:
+- toolchains/llvm/prebuilt/linux-x86_64/bin
+- toolchains/llvm/prebuilt/linux-x86_64/lib