Fixed Android CMake build error (#2486)

`android_native_app_glue.c` wasn't appended to the `raylib_sources` as other libraries were.

Co-authored-by: Patrick Martin <martinpatrick@google.com>

cmake/LibraryConfigurations.cmake

@@ -44,7 +44,7 @@ elseif (${PLATFORM} MATCHES "Android")
     set(PLATFORM_CPP "PLATFORM_ANDROID")
     set(GRAPHICS "GRAPHICS_API_OPENGL_ES2")
     set(CMAKE_POSITION_INDEPENDENT_CODE ON)
-    set(raylib_sources "${raylib_sources} ${ANDROID_NDK}/sources/android/native_app_glue/android_native_app_glue.c")
+    list(APPEND raylib_sources ${ANDROID_NDK}/sources/android/native_app_glue/android_native_app_glue.c)
     add_definitions(-DANDROID -D__ANDROID_API__=21)
     include_directories(${ANDROID_NDK}/sources/android/native_app_glue)
     set(CMAKE_SHARED_LINKER_FLAGS "${CMAKE_SHARED_LINKER_FLAGS} -Wl,--exclude-libs,libatomic.a -Wl,--build-id -Wl,-z,noexecstack -Wl,-z,relro -Wl,-z,now -Wl,--warn-shared-textrel -Wl,--fatal-warnings -u ANativeActivity_onCreate -Wl,-undefined,dynamic_lookup")