Arm backend: Update gcc to 15.2

[perheld]

Signed-off-by: per.held@arm.com
Change-Id: I5c3e9388f3a6d87fd987811d7dc04e9ef85cb69d

cc @digantdesai @freddan80 @per @zingo @oscarandersson8218 @mansnils @Sebastian-Larsson @robell @rascani

[pytorch-bot]

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❌ 2 New Failures, 3 Unrelated Failures

As of commit 1ac00ba with merge base c502916 ():

NEW FAILURES - The following jobs have failed:

• pull / test-arm-cortex-m-size-test (bare_metal) / linux-job (gh)
  RuntimeError: Command docker exec -t ad04b951efdd90a6c0091159eaf01d8384c46e9332329999a3faeb7b50ab60af /exec failed with exit code 1
• pull / unittest / macos / macos-job (gh)
  backends/xnnpack/test/ops/test_conv2d.py::TestConv2d::test_fp16_conv2d

BROKEN TRUNK - The following jobs failed but were present on the merge base:

👉 Rebase onto the `viable/strict` branch to avoid these failures

• pull / unittest / windows / windows-job (gh) (trunk failure)
  backends/xnnpack/test/recipes/test_xnnpack_recipes.py::TestXnnpackRecipes::test_8a4w_recipe
• pull / unittest-editable / windows / windows-job (gh) (trunk failure)
  backends/xnnpack/test/recipes/test_xnnpack_recipes.py::TestXnnpackRecipes::test_8a4w_recipe
• trunk / unittest-release / windows / windows-job (gh) (trunk failure)
  backends/xnnpack/test/recipes/test_xnnpack_recipes.py::TestXnnpackRecipes::test_8a4w_recipe

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[Copilot]

Pull request overview

Updates the Arm backend’s GCC toolchain to Arm GNU Toolchain 15.2.rel1 and adds a targeted build workaround for GCC 15+ when compiling the in-tree flatccrt runtime, keeping builds green under the newer compiler.

Changes:

• Bump Arm GNU toolchain download URLs/dirs/checksums from 13.3.rel1 to 15.2.rel1 in the Arm setup tooling.
• Add a GCC 15+ flatccrt compile option to prevent unterminated-string-initialization warnings from being treated as errors.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
third-party/CMakeLists.txt	Adds a GCC 15+ conditional compile option for flatccrt to avoid a new warning being promoted to an error.
backends/arm/scripts/toolchain_utils.sh	Updates Arm toolchain URL/dir/checksum entries to Arm GNU Toolchain 15.2.rel1 for supported host platforms.

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