Work around flatccrt issue in CI script (#7570)

When running build-qnn-sdk.sh in certain circumstances the libflatccrt.a
cannot be found. To work around this we can build the QNN backend twice,
second time with option `--no_clean`, to make sure the library is found.

Resolves: #7300
Change-Id: I47e14f1fa318538587b848ee02240f7867c88f50

Signed-off-by: Benjamin Klimczak <benjamin.klimczak@arm.com>

.ci/scripts/build-qnn-sdk.sh

@@ -1,5 +1,6 @@
 #!/bin/bash
 # Copyright (c) Meta Platforms, Inc. and affiliates.
+# Copyright 2025 Arm Limited and/or its affiliates.
 # All rights reserved.
 #
 # This source code is licensed under the BSD-style license found in the
@@ -14,7 +15,13 @@ build_qnn_backend() {
   export QNN_SDK_ROOT=/tmp/qnn/2.28.0.241029
   export EXECUTORCH_ROOT="$(cd -- "$(dirname -- "${BASH_SOURCE[0]}")/../.." && pwd)"
 
-  bash backends/qualcomm/scripts/build.sh --skip_aarch64 --job_number 2 --release
+  # Workaround to avoid issues around missing flatccrt library (depending on the
+  # number of jobs used), see issue #7300:
+  # Build twice (second time with `--no_clean`) to make sure libflatccrt.a is
+  # available.
+  # TODO: Remove this workaround once the underlying issue is fixed.
+  bash backends/qualcomm/scripts/build.sh --skip_aarch64 --job_number 2 --release || \
+  bash backends/qualcomm/scripts/build.sh --skip_aarch64 --job_number 2 --release --no_clean
 }
 
 set_up_aot() {