Add riscv64 to Linux wheel build matrix

.ci/requirements-cibw.txt

@@ -1 +1 @@
-cibuildwheel==3.4.0
+cibuildwheel==3.4.1

.github/workflows/wheels-dependencies.sh

@@ -204,6 +204,12 @@ function build_libavif {
             -DAVIF_CODEC_DAV1D=LOCAL
         )
     fi
+    # libaom's riscv64 RVV code calls functions without declarations, which
+    # GCC 14 (manylinux_2_39) treats as errors. Disable arch-specific AOM
+    # optimizations for riscv64; QEMU-based builds don't benefit from them.
+    if [[ "$(uname -m)" == "riscv64" ]]; then
+        libavif_cmake_flags+=(-DAOM_TARGET_CPU=generic)
+    fi
 
     local out_dir=$(fetch_unpack https://github.com/AOMediaCodec/libavif/archive/refs/tags/v$LIBAVIF_VERSION.tar.gz libavif-$LIBAVIF_VERSION.tar.gz)
 
@@ -267,6 +273,13 @@ function build {
     fi
     build_simple libxcb $LIBXCB_VERSION https://www.x.org/releases/individual/lib
 
+    # libjpeg-turbo 3.1.4.1 simdcoverage.c references riscv64 RVV SIMD
+    # functions that are only in upstream main and not yet released. Disable
+    # SIMD for riscv64 to avoid the build error; there is no production
+    # riscv64 SIMD support in this version anyway.
+    if [[ "$(uname -m)" == "riscv64" ]]; then
+        HOST_CMAKE_FLAGS="${HOST_CMAKE_FLAGS} -DWITH_SIMD=FALSE"
+    fi
     build_libjpeg_turbo
     if [[ -n "$IS_MACOS" ]]; then
         # Custom tiff build to include jpeg; by default, configure won't include

.github/workflows/wheels.yml

@@ -39,7 +39,7 @@ concurrency:
   cancel-in-progress: true
 
 env:
-  EXPECTED_DISTS: 66
+  EXPECTED_DISTS: 68
   FORCE_COLOR: 1
 
 jobs:
@@ -94,6 +94,12 @@ jobs:
             os: ubuntu-24.04-arm
             cibw_arch: aarch64
             build: "*musllinux*"
+          - name: "manylinux_2_39 riscv64"
+            platform: linux
+            os: ubuntu-latest
+            cibw_arch: riscv64
+            build: "cp3{12,13}-manylinux*"
+            manylinux: "manylinux_2_39"
           - name: "iOS arm64 device"
             platform: ios
             os: macos-latest
@@ -116,6 +122,12 @@ jobs:
         with:
           python-version: "3.x"
 
+      - name: Set up QEMU
+        if: matrix.cibw_arch == 'riscv64'
+        uses: docker/setup-qemu-action@v4
+        with:
+          platforms: riscv64
+
       - name: Install cibuildwheel
         run: |
           python3 -m pip install -r .ci/requirements-cibw.txt
@@ -128,6 +140,7 @@ jobs:
           CIBW_ARCHS: ${{ matrix.cibw_arch }}
           CIBW_BUILD: ${{ matrix.build }}
           CIBW_ENABLE: cpython-prerelease pypy
+          CIBW_MANYLINUX_RISCV64_IMAGE: ${{ matrix.manylinux }}
           MACOSX_DEPLOYMENT_TARGET: ${{ matrix.macosx_deployment_target }}
 
       - uses: actions/upload-artifact@v7