Make djinterop explicit opt-in.

Add -DDJINTEROP=ON to Ubuntu/CMake travis and appveyor builds.
Add shallow git clone.

.travis.yml

@@ -76,7 +76,7 @@ jobs:
       cache: ccache
       # Ubuntu Bionic build prerequisites
       # TODO for Ubuntu Focal: Replace "-DFAAD=ON" with "-DFFMPEG=ON"
-      env: CMAKEFLAGS_EXTRA="-DFAAD=ON -DLOCALECOMPARE=ON -DMAD=ON -DMODPLUG=ON -DWAVPACK=ON -DWARNINGS_FATAL=ON"
+      env: CMAKEFLAGS_EXTRA="-DDJINTEROP=ON -DFAAD=ON -DLOCALECOMPARE=ON -DMAD=ON -DMODPLUG=ON -DWAVPACK=ON -DWARNINGS_FATAL=ON"
       before_install:
         - export CMAKE_BUILD_PARALLEL_LEVEL="$(nproc)"
         - export CTEST_PARALLEL_LEVEL="$(nproc)"

CMakeLists.txt

@@ -1438,8 +1438,8 @@ if(WIN32)
   target_link_libraries(mixxx-lib PUBLIC FFTW::FFTW)
 endif()
 
-# libdjinterop (enabled only on UNIX for now)
-cmake_dependent_option(DJINTEROP "Use djinterop library" ON "UNIX;NOT APPLE" OFF)
+# libdjinterop (must be enabled explicitly to use)
+option(DJINTEROP "Use djinterop library" OFF)
 if(DJINTEROP)
   message(STATUS "Enabling djinterop support...")
   target_compile_definitions(mixxx-lib PUBLIC __DJINTEROP__)
@@ -1470,6 +1470,7 @@ if(DJINTEROP)
       ExternalProject_Add(libdjinterop
         GIT_REPOSITORY ${DJINTEROP_GIT_REPO_URL}
         GIT_TAG ${DJINTEROP_GIT_TAG}
+        GIT_SHALLOW TRUE
         CONFIGURE_COMMAND meson setup --prefix ${DJINTEROP_INSTALL_DIR} --libdir lib --includedir include build <SOURCE_DIR>
         BUILD_COMMAND meson compile -C build
         INSTALL_COMMAND meson install -C build
@@ -1479,6 +1480,7 @@ if(DJINTEROP)
       ExternalProject_Add(libdjinterop
         GIT_REPOSITORY ${DJINTEROP_GIT_REPO_URL}
         GIT_TAG ${DJINTEROP_GIT_TAG}
+        GIT_SHALLOW TRUE
         INSTALL_DIR ${DJINTEROP_INSTALL_DIR}
         CMAKE_ARGS "-DCMAKE_BUILD_TYPE=${CMAKE_BUILD_TYPE}" -DCMAKE_INSTALL_PREFIX:PATH=<INSTALL_DIR>
         EXCLUDE_FROM_ALL TRUE

appveyor.yml

@@ -115,6 +115,7 @@ for:
       -DBATTERY=ON
       -DBROADCAST=ON
       -DBULK=ON
+      -DDJINTEROP=ON
       -DFFMPEG=ON
       -DHID=ON
       -DLILV=ON