Updating CI for build preset to match CI size test job params

Author: BujSet

.github/workflows/build-presets.yml

@@ -45,14 +45,17 @@ jobs:
       ref: ${{ github.event_name == 'pull_request' && github.event.pull_request.head.sha || github.sha }}
       runner: linux.2xlarge
       docker-image: executorch-ubuntu-22.04-arm-sdk
-      python-version: 3.12
       submodules: recursive
       timeout: 90
       script: |
         set -eux
-        ${CONDA_RUN} ./install_requirements.sh > /dev/null
-        ${CONDA_RUN} cmake --preset ${{ matrix.preset }}
-        ${CONDA_RUN} cmake --build cmake-out -j$(( $(sysctl -n hw.ncpu) - 1 ))
+        # The generic Linux job chooses to use base env, not the one setup by the image
+        CONDA_ENV=$(conda env list --json | jq -r ".envs | .[-1]")
+        conda activate "${CONDA_ENV}"
+
+        ./install_requirements.sh > /dev/null
+        cmake --preset ${{ matrix.preset }}
+        cmake --build cmake-out -j$(( $(nproc) - 1 ))
   linux:
     uses: pytorch/test-infra/.github/workflows/linux_job_v2.yml@main
     strategy: