[teagba] Make TeaGBA (other than the ARM asm) build on all platforms

deps/teagba/src/CMakeLists.txt

@@ -1,18 +1,23 @@
 enable_language(CXX ASM)
 
-set_source_files_properties(gfx.cpp PROPERTIES COMPILE_FLAGS -marm)
-
 add_library(
 	TeaGBA
-		bios.s
-		gba_crt0.s
 		cstartup.cpp
 		gfx.cpp
 )
 
-if(NOT MSVC)
-	target_compile_options(TeaGBA PRIVATE -Wsign-conversion)
-	target_compile_options(TeaGBA PRIVATE -Wconversion)
+if(TURBINE_BUILD_TYPE STREQUAL "GBA")
+	set_source_files_properties(gfx.cpp PROPERTIES COMPILE_FLAGS -marm)
+	target_sources(
+		TeaGBA PRIVATE
+			bios.s
+			gba_crt0.s
+	)
+else()
+	target_sources(
+		TeaGBA PRIVATE
+			bios_stub.cpp
+	)
 endif()
 
 target_include_directories(