meson: fix source file inclusion in libaegisub on osx

libaegisub/meson.build

@@ -58,7 +58,9 @@ if host_machine.system() == 'darwin'
     ]
 else
     libaegisub_src += 'common/dispatch.cpp'
-    if host_machine.system() == 'windows'
+endif
+
+if host_machine.system() == 'windows'
     libaegisub_src += [
         'windows/access.cpp',
         'windows/charset_conv_win.cpp',
@@ -67,7 +69,7 @@ else
         'windows/path_win.cpp',
         'windows/util_win.cpp',
     ]
-    else
+else
     libaegisub_src += [
         'unix/access.cpp',
         'unix/fs.cpp',
@@ -75,7 +77,6 @@ else
         'unix/path.cpp',
         'unix/util.cpp',
     ]
-    endif
 endif
 
 libaegisub_cpp_pch = ['include/lagi_pre.h']