Stage OpenCL-Headers + ICD-Loader before Android OpenCL build

The dockcross/android-arm64 image does not ship OpenCL headers or a stub
libOpenCL.so, so find_package(OpenCL REQUIRED) in ggml-opencl fails.
Add build_opencl_android.sh which clones pinned KhronosGroup
OpenCL-Headers and cross-builds OpenCL-ICD-Loader inside the container,
then passes -DOpenCL_INCLUDE_DIR and -DOpenCL_LIBRARY into the main
project cmake. The device's vendor ICD (Adreno driver) provides the
runtime symbols.

https://claude.ai/code/session_01CQFUfYpg9m65CBt5RRaFRr

Author: claude

.github/build_opencl_android.sh

@@ -0,0 +1,53 @@
+#!/bin/bash
+
+# SPDX-FileCopyrightText: 2026 Bernard Ladenthin <bernard.ladenthin@gmail.com>
+#
+# SPDX-License-Identifier: MIT
+#
+# Android arm64 build with the OpenCL backend enabled and Adreno-tuned
+# kernels embedded. Runs inside the dockcross/android-arm64 container.
+#
+# The dockcross image does not ship OpenCL headers or a libOpenCL.so stub,
+# so this script first stages Khronos OpenCL-Headers and cross-builds
+# OpenCL-ICD-Loader to satisfy `find_package(OpenCL REQUIRED)` at link
+# time. At runtime the device's vendor ICD (e.g. Qualcomm Adreno driver)
+# provides the actual OpenCL symbols.
+
+set -eu
+
+# Forward args to the inner cmake invocation.
+EXTRA_ARGS=("$@")
+
+OPENCL_STAGE=/tmp/opencl-stage
+HEADERS_DIR="$OPENCL_STAGE/OpenCL-Headers"
+LOADER_DIR="$OPENCL_STAGE/OpenCL-ICD-Loader"
+LOADER_BUILD="$LOADER_DIR/build"
+
+# Pinned tags for reproducibility.
+HEADERS_TAG=v2025.07.22
+LOADER_TAG=v2025.07.22
+
+if [ ! -d "$HEADERS_DIR" ]; then
+    mkdir -p "$OPENCL_STAGE"
+    git clone --depth 1 --branch "$HEADERS_TAG" \
+        https://github.com/KhronosGroup/OpenCL-Headers.git "$HEADERS_DIR"
+fi
+
+if [ ! -f "$LOADER_BUILD/libOpenCL.so" ]; then
+    if [ ! -d "$LOADER_DIR" ]; then
+        git clone --depth 1 --branch "$LOADER_TAG" \
+            https://github.com/KhronosGroup/OpenCL-ICD-Loader.git "$LOADER_DIR"
+    fi
+    cmake -B "$LOADER_BUILD" -S "$LOADER_DIR" \
+        -DCMAKE_BUILD_TYPE=Release \
+        -DOPENCL_ICD_LOADER_HEADERS_DIR="$HEADERS_DIR" \
+        -DBUILD_TESTING=OFF
+    cmake --build "$LOADER_BUILD" --config Release -j"$(nproc)"
+fi
+
+mkdir -p build
+cmake -Bbuild \
+    -DOpenCL_INCLUDE_DIR="$HEADERS_DIR" \
+    -DOpenCL_LIBRARY="$LOADER_BUILD/libOpenCL.so" \
+    "${EXTRA_ARGS[@]}"
+cmake --build build --config Release -j"$(nproc)"

.github/workflows/publish.yml

@@ -146,7 +146,7 @@ jobs:
       - name: Build libraries
         shell: bash
         run: |
-          .github/dockcross/dockcross-android-arm64 .github/build.sh "-DANDROID_PLATFORM=android-24 -DOS_NAME=Linux-Android -DOS_ARCH=aarch64 -DGGML_OPENCL=ON -DGGML_OPENCL_EMBED_KERNELS=ON -DGGML_OPENCL_USE_ADRENO_KERNELS=ON"
+          .github/dockcross/dockcross-android-arm64 .github/build_opencl_android.sh "-DANDROID_PLATFORM=android-24 -DOS_NAME=Linux-Android -DOS_ARCH=aarch64 -DGGML_OPENCL=ON -DGGML_OPENCL_EMBED_KERNELS=ON -DGGML_OPENCL_USE_ADRENO_KERNELS=ON"
       - name: Upload artifacts
         uses: actions/upload-artifact@v7
         with:

CLAUDE.md

@@ -61,16 +61,20 @@ Three places wire it together (mirrors the CUDA classifier pattern):
 
 Local sanity build:
 ```bash
-.github/dockcross/dockcross-android-arm64 .github/build.sh \
+.github/dockcross/dockcross-android-arm64 .github/build_opencl_android.sh \
   "-DANDROID_PLATFORM=android-24 -DOS_NAME=Linux-Android -DOS_ARCH=aarch64 \
    -DGGML_OPENCL=ON -DGGML_OPENCL_EMBED_KERNELS=ON \
    -DGGML_OPENCL_USE_ADRENO_KERNELS=ON"
 ```
 Artifacts land in `src/main/resources_android_opencl/net/ladenthin/llama/Linux-Android/aarch64/`.
 
-At runtime the device must provide an OpenCL ICD (`libOpenCL.so`); Qualcomm
-Adreno drivers do. Devices without an ICD should use the default CPU-only
-Android JAR.
+The dockcross image does not ship OpenCL headers or a stub `libOpenCL.so`, so
+`build_opencl_android.sh` first stages Khronos `OpenCL-Headers` and
+cross-builds `OpenCL-ICD-Loader` into `/tmp/opencl-stage/` before invoking the
+main project cmake with `-DOpenCL_INCLUDE_DIR=...` and `-DOpenCL_LIBRARY=...`.
+At runtime the device must provide its own OpenCL ICD (`libOpenCL.so`);
+Qualcomm Adreno drivers do. Devices without an ICD should use the default
+CPU-only Android JAR.
 
 ## Upgrading/Downgrading llama.cpp Version