Replace "depends on PLATFORM_LINUX" with "select PLATFORM_LINUX"

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
diff --git a/coreutils/date.c b/coreutils/date.c
index 05b4f6e..db1b693 100644
--- a/coreutils/date.c
+++ b/coreutils/date.c
@@ -42,7 +42,8 @@
 //config:config FEATURE_DATE_NANO
 //config:	bool "Support %[num]N nanosecond format specifier"
 //config:	default n
-//config:	depends on DATE && PLATFORM_LINUX # syscall(__NR_clock_gettime)
+//config:	depends on DATE  # syscall(__NR_clock_gettime)
+//config:	select PLATFORM_LINUX
 //config:	help
 //config:	  Support %[num]N format specifier. Adds ~250 bytes of code.
 //config: