[nostalgia/core/userland] Enable sign-conversion warning

src/nostalgia/core/userland/CMakeLists.txt

@@ -3,6 +3,8 @@ add_library(
 		media.cpp
 )
 
+target_compile_options(NostalgiaCore-Userspace PRIVATE -Wsign-conversion)
+
 target_link_libraries(
 	NostalgiaCore-Userspace PUBLIC
 		OxFS

src/nostalgia/core/userland/media.cpp

@@ -21,7 +21,7 @@ char *loadRom(const char *path) {
 		return nullptr;
 	}
 
-	const std::size_t size = file.tellg();
+	const auto size = file.tellg();
 	file.seekg(0, std::ios::beg);
 	auto buff = new char[size];
 	file.read(buff, size);