Misc Windows fixes

1. Fix build by making the legacy SSH Storey's secret `logFD` setting
   not a setting on Windows. (It doesn't make sense to specify `void *`
   handles by integer cross-proccess, I don't think.)

2. Move some files that don't need to be Unix-only anymore back to their
   original locations.

src/libstore/legacy-ssh-store.hh

@@ -26,10 +26,14 @@ struct LegacySSHStoreConfig : virtual CommonSSHStoreConfig
 
 struct LegacySSHStore : public virtual LegacySSHStoreConfig, public virtual Store
 {
+#ifndef _WIN32
     // Hack for getting remote build log output.
     // Intentionally not in `LegacySSHStoreConfig` so that it doesn't appear in
     // the documentation
-    const Setting<int> logFD{this, -1, "log-fd", "file descriptor to which SSH's stderr is connected"};
+    const Setting<int> logFD{this, INVALID_DESCRIPTOR, "log-fd", "file descriptor to which SSH's stderr is connected"};
+#else
+    Descriptor logFD = INVALID_DESCRIPTOR;
+#endif
 
     struct Connection;
 

src/libstore/local.mk

@@ -6,7 +6,7 @@ libstore_DIR := $(d)
 
 libstore_SOURCES := $(wildcard $(d)/*.cc $(d)/builtins/*.cc $(d)/build/*.cc)
 ifdef HOST_UNIX
-  libstore_SOURCES += $(wildcard $(d)/unix/*.cc $(d)/unix/builtins/*.cc $(d)/unix/build/*.cc)
+  libstore_SOURCES += $(wildcard $(d)/unix/*.cc $(d)/unix/build/*.cc)
 endif
 ifdef HOST_LINUX
   libstore_SOURCES += $(wildcard $(d)/linux/*.cc)