CI: run the GPU build legs on demand only (#7)

Nothing this workflow builds ships. Our prebuilts come from
unsloth-sd-prebuilt.yml, which is CPU and Apple only by design because GPU
hosts run diffusers/torch. No release here has ever carried a CUDA, ROCm or
Vulkan asset, and build.yml's own release job fails on every push with
"Resource not accessible by integration", so it has never published anything.
Even a forced native GPU load does not use these: install_sd_cpp_prebuilt.py
falls back to leejet upstream when our mirror cannot serve the host.

Measured on run 31238801839, the GPU legs are 561 of 658 minutes, 85% of the
run, and they are the source of the multi-GB artifacts that were filling
Actions storage.

Gated to workflow_dispatch: ubuntu-latest-cmake-vulkan, windows-latest-rocm,
ubuntu-latest-rocm, the container images job, and the cuda12 and vulkan entries
of windows-latest-cmake. What still runs on push and PR is the compile smoke
signal worth keeping: ubuntu-latest-cmake, macOS-latest-cmake and windows CPU,
about 29 minutes.

The matrix entries cannot take a job-level if, so that one uses a fromJSON
ternary. Verified both branches parse back to the original entries with the
defines byte-identical, and that the file is otherwise unchanged outside the
five gates.

Side effect worth knowing: release needs the gated jobs, so on a master push it
now skips instead of failing. It has never succeeded here, so this removes a
standing red X rather than losing a capability. Reverting any single gate
restores the old behaviour for that leg.

Co-authored-by: danielhanchen <unslothshared@gmail.com>

Author: danielhanchen

.github/workflows/build.yml

@@ -116,6 +116,7 @@ jobs:
             sd-${{ env.BRANCH_NAME }}-${{ steps.commit.outputs.short }}-bin-${{ steps.system-info.outputs.OS_TYPE }}-${{ steps.system-info.outputs.OS_NAME }}-${{ steps.system-info.outputs.OS_VERSION }}-${{ steps.system-info.outputs.CPU_ARCH }}.zip
 
   ubuntu-latest-cmake-vulkan:
+    if: ${{ github.event_name == 'workflow_dispatch' }}
     runs-on: ubuntu-latest
 
     steps:
@@ -180,7 +181,7 @@ jobs:
 
   build-and-push-docker-images:
     name: Build and push container images
-    if: ${{ github.event_name != 'pull_request' }}
+    if: ${{ github.event_name == 'workflow_dispatch' }}
     runs-on: ${{ matrix.runner }}
 
     permissions:
@@ -341,13 +342,10 @@ jobs:
 
     strategy:
       matrix:
-        include:
-          - build: "cpu"
-            defines: "-DGGML_NATIVE=OFF -DSD_BUILD_SHARED_LIBS=ON -DSD_BUILD_SHARED_GGML_LIB=ON -DGGML_BACKEND_DL=ON -DGGML_CPU_ALL_VARIANTS=ON"
-          - build: "cuda12"
-            defines: "-DSD_CUDA=ON -DSD_BUILD_SHARED_LIBS=ON -DCMAKE_CUDA_ARCHITECTURES='61;70;75;80;86;89;90;100;120' -DCMAKE_CUDA_FLAGS='-Xcudafe \"--diag_suppress=177\" -Xcudafe \"--diag_suppress=550\"' -DGGML_NATIVE=OFF -DSD_BUILD_SHARED_GGML_LIB=ON -DGGML_BACKEND_DL=ON -DGGML_CPU_ALL_VARIANTS=ON"
-          - build: "vulkan"
-            defines: "-DSD_VULKAN=ON -DSD_BUILD_SHARED_LIBS=ON -DGGML_NATIVE=OFF -DSD_BUILD_SHARED_GGML_LIB=ON -DGGML_BACKEND_DL=ON -DGGML_CPU_ALL_VARIANTS=ON"
+        # cuda12 and vulkan are dispatch-only: nothing here ships (our
+        # prebuilts come from unsloth-sd-prebuilt.yml) and they cost 142 min.
+        include: ${{ github.event_name == 'workflow_dispatch' && fromJSON('[{"build":"cpu","defines":"-DGGML_NATIVE=OFF -DSD_BUILD_SHARED_LIBS=ON -DSD_BUILD_SHARED_GGML_LIB=ON -DGGML_BACKEND_DL=ON -DGGML_CPU_ALL_VARIANTS=ON"},{"build":"cuda12","defines":"-DSD_CUDA=ON -DSD_BUILD_SHARED_LIBS=ON -DCMAKE_CUDA_ARCHITECTURES=''61;70;75;80;86;89;90;100;120'' -DCMAKE_CUDA_FLAGS=''-Xcudafe \"--diag_suppress=177\" -Xcudafe \"--diag_suppress=550\"'' -DGGML_NATIVE=OFF -DSD_BUILD_SHARED_GGML_LIB=ON -DGGML_BACKEND_DL=ON -DGGML_CPU_ALL_VARIANTS=ON"},{"build":"vulkan","defines":"-DSD_VULKAN=ON -DSD_BUILD_SHARED_LIBS=ON -DGGML_NATIVE=OFF -DSD_BUILD_SHARED_GGML_LIB=ON -DGGML_BACKEND_DL=ON -DGGML_CPU_ALL_VARIANTS=ON"}]') || fromJSON('[{"build":"cpu","defines":"-DGGML_NATIVE=OFF -DSD_BUILD_SHARED_LIBS=ON -DSD_BUILD_SHARED_GGML_LIB=ON -DGGML_BACKEND_DL=ON -DGGML_CPU_ALL_VARIANTS=ON"}]') }}
+
     steps:
       - name: Clone
         id: checkout
@@ -446,6 +444,7 @@ jobs:
             sd-${{ env.BRANCH_NAME }}-${{ steps.commit.outputs.short }}-bin-win-${{ matrix.build }}-x64.zip
 
   windows-latest-rocm:
+    if: ${{ github.event_name == 'workflow_dispatch' }}
     runs-on: windows-2022
 
     env:
@@ -577,6 +576,7 @@ jobs:
             sd-${{ env.BRANCH_NAME }}-${{ steps.commit.outputs.short }}-bin-win-rocm-${{ env.ROCM_VERSION }}-x64.zip
 
   ubuntu-latest-rocm:
+    if: ${{ github.event_name == 'workflow_dispatch' }}
     runs-on: ubuntu-24.04
 
     env: