Fix non-Linux builds

Various tools are Linuxish and should thus only attempted to build on
Linux only. Some features are also Linux-only.

Also, libresolv is used on all GNU platforms, notably GNU/Hurd and
GNU/kfreeBSD.

Signed-off-by: Samuel Thibault <samuel.thibault@ens-lyon.org>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
diff --git a/util-linux/acpid.c b/util-linux/acpid.c
index 00613f8..7bce8ab 100644
--- a/util-linux/acpid.c
+++ b/util-linux/acpid.c
@@ -9,6 +9,7 @@
 //config:config ACPID
 //config:	bool "acpid (9 kb)"
 //config:	default y
+//config:	select PLATFORM_LINUX
 //config:	help
 //config:	acpid listens to ACPI events coming either in textual form from
 //config:	/proc/acpi/event (though it is marked deprecated it is still widely