buildbot-build.sh: don't try to copy nonexistent 32-bit libraries.

Test: in aosp-main:
    $ lunch aosp_riscv64-userdebug
    $ echo $ANDROID_PRODUCT_OUT/system/lib
    .../out/target/product/generic_riscv64/system/lib
    $ run 001-HelloWorld on a riscv64 VM

Test: on aosp-master-art:
    $ lunch riscv64
    $ echo $ANDROID_PRODUCT_OUT/system/lib
    .../out/target/product/riscv64/system/lib
    $ run 001-HelloWorld on a riscv64 VM

Change-Id: I90ca549cae4e3c84ba89827cb9e0ec9d3104f2e3

tools/buildbot-build.sh

diff --git a/tools/buildbot-build.sh b/tools/buildbot-build.sh
index 19c9e55..473123d 100755
--- a/tools/buildbot-build.sh
+++ b/tools/buildbot-build.sh
@@ -220,12 +220,12 @@
       arch64=x86_64
     fi
     for so in ${implementation_libs[@]}; do
-      if [ -d "$ANDROID_PRODUCT_OUT/system/lib" ]; then
+      if [ -d "$ANDROID_PRODUCT_OUT/system/lib" -a $arch32 != none ]; then
         cmd="cp -p prebuilts/runtime/mainline/platform/impl/$arch32/${so}.so $ANDROID_PRODUCT_OUT/system/lib/${so}.so"
         msginfo "Executing" "$cmd"
         eval "$cmd"
       fi
-      if [ -d "$ANDROID_PRODUCT_OUT/system/lib64" ]; then
+      if [ -d "$ANDROID_PRODUCT_OUT/system/lib64" -a $arch64 != none ]; then
         cmd="cp -p prebuilts/runtime/mainline/platform/impl/$arch64/${so}.so $ANDROID_PRODUCT_OUT/system/lib64/${so}.so"
         msginfo "Executing" "$cmd"
         eval "$cmd"