CMakeLists: Derive the source directory grouping from targets themselves

Removes the need to store to separate SRC and HEADER variables,
and then construct the target in most cases.

src/audio_core/CMakeLists.txt

@@ -1,40 +1,33 @@
-set(SRCS
-            audio_core.cpp
-            codec.cpp
-            hle/dsp.cpp
-            hle/filter.cpp
-            hle/mixers.cpp
-            hle/pipe.cpp
-            hle/source.cpp
-            interpolate.cpp
-            sink_details.cpp
-            time_stretch.cpp
-            )
+add_library(audio_core STATIC
+    audio_core.cpp
+    audio_core.h
+    codec.cpp
+    codec.h
+    hle/common.h
+    hle/dsp.cpp
+    hle/dsp.h
+    hle/filter.cpp
+    hle/filter.h
+    hle/mixers.cpp
+    hle/mixers.h
+    hle/pipe.cpp
+    hle/pipe.h
+    hle/source.cpp
+    hle/source.h
+    interpolate.cpp
+    interpolate.h
+    null_sink.h
+    sink.h
+    sink_details.cpp
+    sink_details.h
+    time_stretch.cpp
+    time_stretch.h
 
-set(HEADERS
-            audio_core.h
-            codec.h
-            hle/common.h
-            hle/dsp.h
-            hle/filter.h
-            hle/mixers.h
-            hle/pipe.h
-            hle/source.h
-            interpolate.h
-            null_sink.h
-            sink.h
-            sink_details.h
-            time_stretch.h
-            )
+    $<$<BOOL:SDL2_FOUND>:sdl2_sink.cpp sdl2_sink.h>
+)
 
-if(SDL2_FOUND)
-    set(SRCS ${SRCS} sdl2_sink.cpp)
-    set(HEADERS ${HEADERS} sdl2_sink.h)
-endif()
+create_target_directory_groups(audio_core)
 
-create_directory_groups(${SRCS} ${HEADERS})
-
-add_library(audio_core STATIC ${SRCS} ${HEADERS})
 target_link_libraries(audio_core PUBLIC common core)
 target_link_libraries(audio_core PRIVATE SoundTouch)