[common/dynamic_library] fix AUR build error (#4156)

not gonna question why there was an ifdef there

Signed-off-by: lizzie <lizzie@eden-emu.dev>

Reviewed-on: https://git.eden-emu.dev/eden-emu/eden/pulls/4156
Reviewed-by: CamilleLaVey <camillelavey99@gmail.com>
Reviewed-by: MaranBr <maranbr@eden-emu.dev>

src/common/dynamic_library.cpp

@@ -5,11 +5,7 @@
 // SPDX-License-Identifier: GPL-2.0-or-later
 
 #include <string>
-
-#ifndef _WIN32
 #include <cstring>
-#endif
-
 #include <utility>
 
 #include <fmt/ranges.h>