ci: Introduce artifacts

Separates `test-linux` into `build-linux` and `test-linux`, wherein `build-` builds out of tree, and uploading the build for the `test-` job.
Tar compression is done to retain execution permissions when downloading build artifact.
When calling `make test`, override `TARGETS` and `EXTRA_TARGETS` to prevent rebuild.

.github/workflows/test-linux.yml

@@ -1,9 +1,15 @@
 name: Build and run tests (Linux)
 
-on: [push, pull_request]
+on:
+  pull_request:
+    branches:
+    - master
+  push:
+    branches:
+    - master
 
 jobs:
-  test-linux:
+  build-linux:
     runs-on: ${{ matrix.os.id }}
     strategy:
       matrix:
@@ -14,17 +20,6 @@ jobs:
           - 'gcc-11'
         cpp_std:
           - 'c++11'
-          - 'c++14'
-          - 'c++17'
-          - 'c++20'
-        include:
-          # Limit the older compilers to C++11 mode
-          - os: { id: ubuntu-20.04, name: focal }
-            compiler: 'clang-11'
-            cpp_std: 'c++11'
-          - os: { id: ubuntu-20.04, name: focal }
-            compiler: 'gcc-10'
-            cpp_std: 'c++11'
       fail-fast: false
     steps:
       - name: Install Dependencies
@@ -107,14 +102,57 @@ jobs:
           make -j${{ env.procs }}
           make install
 
-      - name: Build yosys
+      - name: Build yosys out-of-tree
         shell: bash
         run: |
-          make config-${CC%%-*}
-          make -j${{ env.procs }} CCXXSTD=${{ matrix.cpp_std }} CC=$CC CXX=$CC LD=$CC
+          mkdir build
+          cd build
+          make -f ../Makefile config-${CC%%-*}
+          make -f ../Makefile -j${{ env.procs }} CXXSTD=${{ matrix.cpp_std }} CC=$CC CXX=$CC LD=$CC
 
-      - name: Run tests
+      - name: Compress build
+        shell: bash
+        run: |
+          cd build
+          tar -cvf ../build.tar Makefile.conf share/ yosys yosys-*
+
+      - name: Store build artifact
         if: (matrix.cpp_std == 'c++11') && (matrix.compiler == 'gcc-11')
+        uses: actions/upload-artifact@v4
+        with:
+          name: build-artifact
+          path: build.tar
+          retention-days: 1
+
+  test-linux:
+    name: Run tests
+    needs: build-linux
+    runs-on: ubuntu-latest
+    steps:
+      - name: Install Dependencies
+        shell: bash
+        run: |
+          sudo apt-get update
+          sudo apt-get install gperf build-essential bison flex libreadline-dev gawk tcl-dev libffi-dev git graphviz xdot pkg-config python3 libboost-system-dev libboost-python-dev libboost-filesystem-dev zlib1g-dev
+
+      - name: Runtime environment
+        shell: bash
+        env:
+          WORKSPACE: ${{ github.workspace }}
+        run: |
+          echo "procs=$(nproc)" >> $GITHUB_ENV
+
+      - name: Download build artifact
+        uses: actions/download-artifact@v4
+        with:
+          name: build-artifact
+
+      - name: Uncompress build
+        shell: bash
+        run:
+          tar -xvf build.tar
+
+      - name: Run tests
         shell: bash
         run: |
-          make -j${{ env.procs }} test CXXSTD=${{ matrix.cpp_std }} CC=$CC CXX=$CC LD=$CC
+          make -j${{ env.procs }} test TARGETS= EXTRA_TARGETS=

.github/workflows/test-macos.yml

@@ -1,6 +1,12 @@
 name: Build and run tests (macOS)
 
-on: [push, pull_request]
+on:
+  pull_request:
+    branches:
+    - master
+  push:
+    branches:
+    - master
 
 jobs:
   test-macos:
@@ -11,7 +17,6 @@ jobs:
           - { id: macos-13, name: 'Ventura' }
         cpp_std:
           - 'c++11'
-          - 'c++17'
       fail-fast: false
     steps:
       - name: Install Dependencies