samples: vfs: build sample programs for target architecture

These userspace programs include UAPI headers exported to usr/include/.
'make headers' always works for the target architecture (i.e. the same
architecture as the kernel), so the sample programs should be built for
the target as well. Kbuild now supports 'userprogs' for that.

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

samples/Kconfig

@@ -184,7 +184,7 @@ config SAMPLE_ANDROID_BINDERFS
 
 config SAMPLE_VFS
 	bool "Build example programs that use new VFS system calls"
-	depends on HEADERS_INSTALL
+	depends on CC_CAN_LINK && HEADERS_INSTALL
 	help
 	  Build example userspace programs that use new VFS system calls such
 	  as mount API and statx().  Note that this is restricted to the x86

samples/vfs/Makefile

 # SPDX-License-Identifier: GPL-2.0-only
-# List of programs to build
-hostprogs := \
-	test-fsmount \
-	test-statx
+userprogs := test-fsmount test-statx
+always-y := $(userprogs)
 
-always-y := $(hostprogs)
-
-HOSTCFLAGS_test-fsmount.o += -I$(objtree)/usr/include
-HOSTCFLAGS_test-statx.o += -I$(objtree)/usr/include
+userccflags += -I usr/include