Increase the number of 'X' characters in calls to `mktemp`, for portability.

On OpenBSD, using only five 'X' characters results in the following error message:

mktemp: insufficient number of Xs in template `tmp_bazel_zip_files_XXXXX'

On OpenBSD, the minimum number of 'X' characters is six:
https://man.openbsd.org/mktemp

PiperOrigin-RevId: 315462488
diff --git a/src/create_java_tools_release.sh b/src/create_java_tools_release.sh
index 9376b0a..eb16086 100755
--- a/src/create_java_tools_release.sh
+++ b/src/create_java_tools_release.sh
@@ -67,7 +67,7 @@
 
 # Create a tmp directory to download the artifacts from GCS and compute their
 # sha256sum.
-tmp_dir=$(mktemp -d -t 'tmp_bazel_zip_files_XXXXX')
+tmp_dir=$(mktemp -d -t 'tmp_bazel_zip_files_XXXXXX')
 trap "rm -fr $tmp_dir" EXIT
 
 gcs_bucket="gs://bazel-mirror/bazel_java_tools"
diff --git a/src/merge_zip_files.sh b/src/merge_zip_files.sh
index c148a9a..6850196 100755
--- a/src/merge_zip_files.sh
+++ b/src/merge_zip_files.sh
@@ -49,7 +49,7 @@
 
 initial_pwd="$(pwd)"
 
-tmp_dir=$(mktemp -d -t 'tmp_bazel_zip_files_XXXXX')
+tmp_dir=$(mktemp -d -t 'tmp_bazel_zip_files_XXXXXX')
 trap "rm -fr $tmp_dir" EXIT
 tmp_zip="$tmp_dir/archive.zip"
 
diff --git a/src/upload_java_tools.sh b/src/upload_java_tools.sh
index 11b5a1e..4e21358 100755
--- a/src/upload_java_tools.sh
+++ b/src/upload_java_tools.sh
@@ -80,7 +80,7 @@
 
 # Create a temp directory and a writable temp zip file to add a README.md file to
 # the initial zip.
-tmp_dir=$(mktemp -d -t 'tmp_bazel_zip_files_XXXXX')
+tmp_dir=$(mktemp -d -t 'tmp_bazel_zip_files_XXXXXX')
 trap "rm -fr $tmp_dir" EXIT
 tmp_zip="$tmp_dir/archive.zip"
 
diff --git a/src/zip_files.sh b/src/zip_files.sh
index 73926e5..1422a6c 100755
--- a/src/zip_files.sh
+++ b/src/zip_files.sh
@@ -31,7 +31,7 @@
 
 initial_pwd="$(pwd)"
 
-tmp_dir=$(mktemp -d -t 'tmp_bazel_zip_files_XXXXX')
+tmp_dir=$(mktemp -d -t 'tmp_bazel_zip_files_XXXXXX')
 trap "rm -fr $tmp_dir" EXIT
 tmp_zip="$tmp_dir/archive.zip"