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/tests/CMakeLists.txt

@@ -1,20 +1,16 @@
-set(SRCS
-            common/param_package.cpp
-            core/arm/arm_test_common.cpp
-            core/core_timing.cpp
-            core/file_sys/path_parser.cpp
-            core/memory/memory.cpp
-            glad.cpp
-            tests.cpp
-            )
+add_executable(tests
+    common/param_package.cpp
+    core/arm/arm_test_common.cpp
+    core/arm/arm_test_common.h
+    core/core_timing.cpp
+    core/file_sys/path_parser.cpp
+    core/memory/memory.cpp
+    glad.cpp
+    tests.cpp
+)
 
-set(HEADERS
-            core/arm/arm_test_common.h
-            )
+create_target_directory_groups(tests)
 
-create_directory_groups(${SRCS} ${HEADERS})
-
-add_executable(tests ${SRCS} ${HEADERS})
 target_link_libraries(tests PRIVATE common core)
 target_link_libraries(tests PRIVATE glad) # To support linker work-around
 target_link_libraries(tests PRIVATE ${PLATFORM_LIBRARIES} catch-single-include Threads::Threads)