[fdk-aac] update osx triplet to build a dynamic library

overlay/triplets/x64-osx.cmake

@@ -1,6 +1,14 @@
 set(VCPKG_TARGET_ARCHITECTURE x64)
 set(VCPKG_CRT_LINKAGE dynamic)
-set(VCPKG_LIBRARY_LINKAGE static)
+
+# Mixxx loads fdk-aac dynamically at runtime. This allows the user to replace 
+# the version of fdk-aac we ship which has the patent-encumbered HE-AAC 
+#removed with another build that supports HE-AAC.
+if(${PORT} MATCHES "fdk-aac")
+    set(VCPKG_LIBRARY_LINKAGE dynamic)
+else()
+    set(VCPKG_LIBRARY_LINKAGE static)
+endif()
 
 set(VCPKG_CMAKE_SYSTEM_NAME Darwin)
 set(VCPKG_OSX_ARCHITECTURES x86_64)