support CMake older than 3.19 which doesn't allow defining INTERFACE …

…library type with explicit source list

packager/utils/CMakeLists.txt

@@ -4,8 +4,9 @@
 # license that can be found in the LICENSE file or at
 # https://developers.google.com/open-source/licenses/bsd
 
-add_library(utils_clock INTERFACE
-  clock.h)
+add_library(utils_clock STATIC
+  clock.h
+  clock.cc)
 
 add_library(utils_test_clock STATIC
   test_clock.cc

packager/utils/clock.cc

@@ -0,0 +1,9 @@
+#import "packager/utils/clock.h"
+
+namespace shaka {
+
+    Clock::time_point Clock::now() noexcept {
+        return std::chrono::system_clock::now();
+    }
+
+}

packager/utils/clock.h

@@ -17,7 +17,7 @@ class Clock {
 
   virtual ~Clock() = default;
 
-  virtual time_point now() noexcept { return std::chrono::system_clock::now(); }
+  virtual time_point now() noexcept;
 };
 
 }  // namespace shaka