Make a few commands that were Unix-only no longer

Also clean up some more linux-specific (`setPersonality`) code in
alignment with recent best practices.

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

@@ -14,7 +14,6 @@
 #include "topo-sort.hh"
 #include "callback.hh"
 #include "json-utils.hh"
-#include "personality.hh"
 #include "current-process.hh"
 #include "child.hh"
 #include "unix-domain-socket.hh"
@@ -52,6 +51,7 @@
 # endif
 # define pivot_root(new_root, put_old) (syscall(SYS_pivot_root, new_root, put_old))
 # include "cgroup.hh"
+# include "personality.hh"
 #endif
 
 #if __APPLE__
@@ -1957,7 +1957,9 @@ void LocalDerivationGoal::runChild()
         /* Close all other file descriptors. */
         closeMostFDs({STDIN_FILENO, STDOUT_FILENO, STDERR_FILENO});
 
-        setPersonality(drv->platform);
+#if __linux__
+        linux::setPersonality(drv->platform);
+#endif
 
         /* Disable core dumps by default. */
         struct rlimit limit = { 0, RLIM_INFINITY };

src/libstore/unix/build/personality.cc

@@ -1,45 +0,0 @@
-#include "personality.hh"
-#include "globals.hh"
-
-#if __linux__
-#include <sys/utsname.h>
-#include <sys/personality.h>
-#endif
-
-#include <cstring>
-
-namespace nix {
-
-void setPersonality(std::string_view system)
-{
-#if __linux__
-        /* Change the personality to 32-bit if we're doing an
-           i686-linux build on an x86_64-linux machine. */
-        struct utsname utsbuf;
-        uname(&utsbuf);
-        if ((system == "i686-linux"
-                && (std::string_view(SYSTEM) == "x86_64-linux"
-                    || (!strcmp(utsbuf.sysname, "Linux") && !strcmp(utsbuf.machine, "x86_64"))))
-            || system == "armv7l-linux"
-            || system == "armv6l-linux"
-            || system == "armv5tel-linux")
-        {
-            if (personality(PER_LINUX32) == -1)
-                throw SysError("cannot set 32-bit personality");
-        }
-
-        /* Impersonate a Linux 2.6 machine to get some determinism in
-           builds that depend on the kernel version. */
-        if ((system == "i686-linux" || system == "x86_64-linux") && settings.impersonateLinux26) {
-            int cur = personality(0xffffffff);
-            if (cur != -1) personality(cur | 0x0020000 /* == UNAME26 */);
-        }
-
-        /* Disable address space randomization for improved
-           determinism. */
-        int cur = personality(0xffffffff);
-        if (cur != -1) personality(cur | ADDR_NO_RANDOMIZE);
-#endif
-}
-
-}

src/libstore/unix/build/personality.hh

@@ -1,12 +0,0 @@
-#pragma once
-///@file
-
-#include <string>
-
-namespace nix {
-
-void setPersonality(std::string_view system);
-
-}
-
-