cmake: Defer test subproject until after defining install/uninstall

It looks as though something in the test subproject "leaks" into the
main build system, causing us to try to install ${builddir}/test/sdl2.pc
instead of the correct ${builddir}/sdl2.pc. Moving the tests subproject
further down avoids this.

Resolves: https://github.com/libsdl-org/SDL/issues/5604
Signed-off-by: Simon McVittie <[email protected]>

CMakeLists.txt

@@ -2965,7 +2965,6 @@ if(SDL_TEST)
   include_directories(AFTER "${SDL2_SOURCE_DIR}/include")
   file(GLOB TEST_SOURCES ${SDL2_SOURCE_DIR}/src/test/*.c)
   add_library(SDL2_test STATIC ${TEST_SOURCES})
-  add_subdirectory(test)
 endif()
 
 ##### Installation targets #####
@@ -3091,3 +3090,8 @@ if(NOT SDL2_DISABLE_UNINSTALL)
   endif()
 endif()
 
+##### Tests subproject (must appear after the install/uninstall targets) #####
+
+if(SDL_TEST)
+  add_subdirectory(test)
+endif()