Revert "std.process: further totalSystemMemory portage"

This reverts commit 5c70d7b.

Author: andrewrk

lib/std/process.zig

@@ -1163,17 +1163,12 @@ pub fn totalSystemMemory() TotalSystemMemoryError!usize {
         .linux => {
             return totalSystemMemoryLinux() catch return error.UnknownTotalSystemMemory;
         },
-        .freebsd, .netbsd, .dragonfly, .macos => {
+        .freebsd => {
             var physmem: c_ulong = undefined;
             var len: usize = @sizeOf(c_ulong);
-            const name = switch (builtin.os.tag) {
-                .macos => "hw.memsize",
-                .netbsd => "hw.physmem64",
-                else => "hw.physmem",
-            };
-            os.sysctlbynameZ(name, &physmem, &len, null, 0) catch |err| switch (err) {
+            os.sysctlbynameZ("hw.physmem", &physmem, &len, null, 0) catch |err| switch (err) {
                 error.NameTooLong, error.UnknownName => unreachable,
-                else => return error.UnknownTotalSystemMemory,
+                else => |e| return e,
             };
             return @as(usize, @intCast(physmem));
         },