Update macos build instructions in Jenkinsfile and build.yml

.github/workflows/build.yml

@@ -85,8 +85,13 @@ jobs:
       if: matrix.os == 'macos-12'
       run: |
         brew install ccache gcc@12 llvm boost fftw hdf5 open-mpi openblas
-        pip3 install mako numpy scipy mpi4py
-        pip3 install -r requirements.txt
+        mkdir $HOME/.venv
+        python3 -m venv $HOME/.venv/my_python
+        source $HOME/.venv/my_python/bin/activate
+        pip install mako numpy scipy mpi4py
+        pip install -r requirements.txt
+        echo "VIRTUAL_ENV=$VIRTUAL_ENV" >> $GITHUB_ENV
+        echo "PATH=$PATH" >> $GITHUB_ENV
 
     - name: add clang cxxflags
       if: ${{ contains(matrix.cxx, 'clang') }}

Jenkinsfile

@@ -89,6 +89,7 @@ for (int i = 0; i < osxPlatforms.size(); i++) {
           "LD_LIBRARY_PATH=$hdf5/lib",
           "PYTHONPATH=$installDir/lib/python3.9/site-packages",
           "CMAKE_PREFIX_PATH=$venv/lib/cmake/triqs",
+          "VIRTUAL_ENV=$venv",
           "OMP_NUM_THREADS=2"]) {
         deleteDir()
         /* note: this is installing into the parent (triqs) venv (install dir), which is thus shared among apps and so not be completely safe */