fix: add Bazel option to force creating bazel-bin symlink (googleapis…

…#5183)

Fixes googleapis#5185.

These `bazel-*` symlinks add a lot of toil for human users, and we are
thinking of disabling them in .bazelrc. Since this code depends on them
being created, let's have them enabled explicitly in the script.

`BAZEL_FLAGS` is not the right place for it, because this is not
something that is supposed to be configured, but rather something that
is supposed to be hardcoded.

---------

Co-authored-by: Jeff Ching <chingor@google.com>
Co-authored-by: Jeffrey Rennie <rennie@google.com>
Co-authored-by: Benjamin E. Coe <bencoe@google.com>

packages/bazel-bot/docker-image/generate-googleapis-gen.sh

@@ -89,7 +89,12 @@ for (( idx=${#ungenerated_shas[@]}-1 ; idx>=0 ; idx-- )) ; do
         targets="$BUILD_TARGETS"
     fi
     # Clean out all the source packages from the previous build.
-    rm -f $(find -L "$GOOGLEAPIS/bazel-bin" -name "*.tar.gz")
+
+    BAZEL_BIN=$(cd "$GOOGLEAPIS" && bazel info bazel-bin)
+    # The directory might not exist before the build, but its path is known
+    if test -d "$BAZEL_BIN"; then
+      rm -f $(find "$BAZEL_BIN" -name "*.tar.gz")
+    fi
     # Confirm that bazel can fetch remote build dependencies before building
     # with -k.  Otherwise, we can't distinguish a build failure due to a bad proto
     # vs. a build failure due to transient network issue.
@@ -108,7 +113,7 @@ for (( idx=${#ungenerated_shas[@]}-1 ; idx>=0 ; idx-- )) ; do
     # Clear out the existing contents of googleapis-gen before we copy back into it,
     # so that deleted APIs will be be removed.
     rm -rf "$GOOGLEAPIS_GEN/external" "$GOOGLEAPIS_GEN/google" "$GOOGLEAPIS_GEN/grafeas"
-    
+
     # Untar the generated source files into googleapis-gen.
     let target_count=0
     failed_targets=()
@@ -119,7 +124,7 @@ for (( idx=${#ungenerated_shas[@]}-1 ; idx>=0 ; idx-- )) ; do
         parent_dir=$(dirname $tar_gz)
         target_dir="$GOOGLEAPIS_GEN/$parent_dir"
         mkdir -p "$target_dir"
-        tar -xf "$GOOGLEAPIS/bazel-bin/$tar_gz" -C "$target_dir" || {
+        tar -xf "$BAZEL_BIN/$tar_gz" -C "$target_dir" || {
             failed_targets+=($target)
             # Restore the original source code because bazel failed to generate
             # the new source code.