CI: cache AJA build [Win]

Since we must now build the new libajantv2, which takes some 3 minutes,
cache the build in order not to increase the build time.

Also use libajantv2 path for the SDK instead of AJA (doesn't require
unneeded rename), which will be Windows specific.

Only do it in MSW, since the build is slowest. But it can be easily used
also for other platforms.

.github/scripts/install-common-deps.sh

@@ -35,22 +35,25 @@ download_install_cineform() {(
         sudo cmake --install .
 )}
 
-install_aja() {(
+download_build_aja() {
         git clone --depth 1 https://github.com/aja-video/libajantv2.git
-        cd libajantv2
         export MACOSX_DEPLOYMENT_TARGET=10.13 # needed for arm64 mac
         cmake -DAJANTV2_DISABLE_DEMOS=ON  -DAJANTV2_DISABLE_DRIVER=ON \
                 -DAJANTV2_DISABLE_TOOLS=ON  -DAJANTV2_DISABLE_TESTS=ON \
                 -DAJANTV2_DISABLE_PLUGINS=ON  -DAJANTV2_BUILD_SHARED=ON \
-                -DCMAKE_BUILD_TYPE=Release -Bbuild -S.
-        cmake --build build --config Release -j "$(nproc)"
+                -DCMAKE_BUILD_TYPE=Release -Blibajantv2/build -Slibajantv2
+        cmake --build libajantv2/build --config Release -j "$(nproc)"
+}
+
+install_aja() {(
+        if [ ! -d libajantv2 ]; then
+                download_build_aja
+        fi
         if is_win; then
-                cp build/ajantv2/Release/ajantv2.dll /usr/local/bin/
-                cp build/ajantv2/Release/ajantv2.lib /usr/local/lib/
-                cd ..
-                mv libajantv2 "$GITHUB_WORKSPACE/AJA"
+                cp libajantv2/build/ajantv2/Release/ajantv2.dll /usr/local/bin/
+                cp libajantv2/build/ajantv2/Release/ajantv2.lib /usr/local/lib/
         else
-                sudo cmake --install build
+                sudo cmake --install libajantv2/build
         fi
 )}