samples: timers: use 'userprogs' syntax

Kbuild now supports the 'userprogs' syntax to compile userspace
programs for the same architecture as the kernel.

Add the entry to samples/Makefile to put this into the build bot
coverage.

I also added the CONFIG option guarded by 'depends on CC_CAN_LINK'
because $(CC) may not provide libc.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Acked-by: Sam Ravnborg <sam@ravnborg.org>

samples/Kconfig

@@ -135,6 +135,10 @@ config SAMPLE_SECCOMP
 	  Build samples of seccomp filters using various methods of
 	  BPF filter construction.
 
+config SAMPLE_TIMER
+	bool "Timer sample"
+	depends on CC_CAN_LINK && HEADERS_INSTALL
+
 config SAMPLE_UHID
 	bool "UHID sample"
 	depends on CC_CAN_LINK && HEADERS_INSTALL

samples/Makefile

@@ -16,6 +16,7 @@ subdir-$(CONFIG_SAMPLE_PIDFD)		+= pidfd
 obj-$(CONFIG_SAMPLE_QMI_CLIENT)		+= qmi/
 obj-$(CONFIG_SAMPLE_RPMSG_CLIENT)	+= rpmsg/
 subdir-$(CONFIG_SAMPLE_SECCOMP)		+= seccomp
+subdir-$(CONFIG_SAMPLE_TIMER)		+= timers
 obj-$(CONFIG_SAMPLE_TRACE_EVENTS)	+= trace_events/
 obj-$(CONFIG_SAMPLE_TRACE_PRINTK)	+= trace_printk/
 obj-$(CONFIG_SAMPLE_FTRACE_DIRECT)	+= ftrace/

samples/timers/Makefile

 # SPDX-License-Identifier: GPL-2.0
-ifndef CROSS_COMPILE
-uname_M := $(shell uname -m 2>/dev/null || echo not)
-ARCH ?= $(shell echo $(uname_M) | sed -e s/i.86/x86/ -e s/x86_64/x86/)
+userprogs := hpet_example
+always-y := $(userprogs)
 
-ifeq ($(ARCH),x86)
-CC := $(CROSS_COMPILE)gcc
-PROGS := hpet_example
-
-all: $(PROGS)
-
-clean:
-	rm -fr $(PROGS)
-
-endif
-endif
+userccflags += -I usr/include