github: try to fix Linux workflow

Author: deniskovalchuk

.github/workflows/linux.yml

@@ -15,15 +15,39 @@ jobs:
     steps:
     - uses: actions/checkout@v3
 
+    - name: Cache externals
+      id: cache-externals
+      uses: actions/cache@v3
+      with:
+        path: ${{runner.temp}}/boost_1_88_0
+        key: cache-externals
+
     - name: Get externals
+      if: steps.cache-externals.outputs.cache-hit != 'true'
+      working-directory: ${{runner.temp}}
       run: |
-        sudo apt-get install g++-10 libboost-all-dev
+        sudo apt-get install g++-10
         pip3 install pyOpenSSL
+        # Download Boost.
+        wget https://archives.boost.io/release/1.88.0/source/boost_1_88_0.tar.gz
+        # Extract.
+        tar -xvzf boost_1_88_0.tar.gz
+        # Build.
+        cd boost_1_88_0
+        ./bootstrap.sh
+        ./b2 link=static
 
     - name: Build
+      env:
+        BOOST_ROOT: ${{runner.temp}}/boost_1_88_0
+        Boost_INCLUDE_DIR: ${{runner.temp}}/boost_1_88_0/libs/headers
       run: |
         mkdir -p build/release
-        cmake -S . -B build/release -DCMAKE_BUILD_TYPE=Release -DCMAKE_CXX_COMPILER=g++-10
+        cmake -S . -B build/release `
+              -DCMAKE_BUILD_TYPE=Release `
+              -DCMAKE_CXX_COMPILER=g++-10 `
+              -DBoost_USE_STATIC_LIBS=ON `
+              -DBoost_DIR="$BOOST_ROOT/stage/lib/cmake/Boost-1.88.0"
         cmake --build build/release
 
     - name: Test libftp