ci: run full test suite in the Alpine (musl) job

Clone grok-test-data and build with BUILD_TESTING=ON + GRK_DATA_ROOT so
the static musl job runs ctest like the other matrix jobs (replacing the
build-only smoke check). Validated locally: 1730/1730 pass on Alpine musl.

Author: Grok Compression

.github/workflows/build.yml

@@ -186,27 +186,26 @@ jobs:
     - uses: actions/checkout@v4
       with:
         submodules: true
-    - name: static build + smoke test in Alpine (musl) container
+    - name: static build + test in Alpine (musl) container
       run: |
         docker run --rm -v "$PWD":/src -w /src alpine:3.20 sh -c '
           set -e
           apk add --no-cache build-base cmake git bash perl nasm linux-headers python3
+          git clone --depth=1 --branch=master \
+            https://github.com/GrokImageCompression/grok-test-data.git /tmp/grok-test-data
           cmake -S . -B build-alpine \
             -DCMAKE_BUILD_TYPE=Release \
             -DBUILD_SHARED_LIBS=OFF \
-            -DBUILD_TESTING=OFF \
+            -DBUILD_TESTING=ON \
             -DGRK_ENABLE_LIBCURL=OFF \
             -DGRK_BUILD_CODEC=ON \
+            -DGRK_DATA_ROOT=/tmp/grok-test-data \
             -DCMAKE_EXE_LINKER_FLAGS=-static
           cmake --build build-alpine -j"$(nproc)"
           if ldd build-alpine/bin/grk_compress >/dev/null 2>&1; then
             echo "ERROR: grk_compress is not statically linked"; exit 1
           fi
           echo "confirmed fully static musl binary"
-          printf "P5\n2 2\n255\n" > /tmp/t.pgm
-          printf "\x00\x40\x80\xc0" >> /tmp/t.pgm
-          ./build-alpine/bin/grk_compress -i /tmp/t.pgm -o /tmp/t.jp2
-          ./build-alpine/bin/grk_decompress -i /tmp/t.jp2 -o /tmp/out.pgm
-          echo "PNM round-trip OK on musl"
+          ctest --test-dir build-alpine --output-on-failure
         '