Add "Show build environment" step

Show version of compiler and ccache being used.

.github/workflows/ci.yml

@@ -116,7 +116,7 @@ jobs:
         with:
           key: ${{ matrix.name }}
 
-      - name: Set up build system
+      - name: Set up build environment
         run: |
           echo LD_LIBRARY_PATH=`pwd`/lib >> $GITHUB_ENV
 
@@ -162,6 +162,20 @@ jobs:
 
           ./build/tools/before_install.sh
 
+      - name: Show build environment
+        run: |
+          echo "Environment:"
+          env | sort
+          echo
+
+          echo "Compiler version:"
+          ${CXX-g++} --version
+          echo
+
+          echo "Ccache version:"
+          ccache --version
+          echo
+
       - name: Configuring
         run: |
           wxCONFIGURE_OPTIONS="--disable-optimise $wxCONFIGURE_FLAGS"