Start factoring out Unix assumptions

This splits files and adds new identifiers in preperation for supporting
windows, but no Windows-specific code is actually added yet.

Co-authored-by: Robert Hensing <roberth@users.noreply.github.com>

src/libstore/build/local-derivation-goal.cc

@@ -17,7 +17,6 @@
 #include "cgroup.hh"
 #include "personality.hh"
 #include "current-process.hh"
-#include "namespaces.hh"
 #include "child.hh"
 #include "unix-domain-socket.hh"
 #include "posix-fs-canonicalise.hh"
@@ -40,18 +39,19 @@
 
 /* Includes required for chroot support. */
 #if __linux__
-#include <sys/ioctl.h>
-#include <net/if.h>
-#include <netinet/ip.h>
-#include <sys/mman.h>
-#include <sched.h>
-#include <sys/param.h>
-#include <sys/mount.h>
-#include <sys/syscall.h>
-#if HAVE_SECCOMP
-#include <seccomp.h>
-#endif
-#define pivot_root(new_root, put_old) (syscall(SYS_pivot_root, new_root, put_old))
+# include <sys/ioctl.h>
+# include <net/if.h>
+# include <netinet/ip.h>
+# include <sys/mman.h>
+# include <sched.h>
+# include <sys/param.h>
+# include <sys/mount.h>
+# include <sys/syscall.h>
+# include "namespaces.hh"
+# if HAVE_SECCOMP
+#   include <seccomp.h>
+# endif
+# define pivot_root(new_root, put_old) (syscall(SYS_pivot_root, new_root, put_old))
 #endif
 
 #if __APPLE__

src/libstore/filetransfer.cc

@@ -1,5 +1,4 @@
 #include "filetransfer.hh"
-#include "namespaces.hh"
 #include "globals.hh"
 #include "store-api.hh"
 #include "s3.hh"
@@ -12,6 +11,10 @@
 #include <aws/core/client/ClientConfiguration.h>
 #endif
 
+#if __linux__
+# include "namespaces.hh"
+#endif
+
 #include <unistd.h>
 #include <fcntl.h>
 
@@ -568,7 +571,9 @@ struct curlFileTransfer : public FileTransfer
             stopWorkerThread();
         });
 
+        #if __linux__
         unshareFilesystem();
+        #endif
 
         std::map<CURL *, std::shared_ptr<TransferItem>> items;