Commit 5318321d36 ("samples: disable CONFIG_SAMPLES for UML") used
a big hammer to fix the build errors under the samples/ directory.
Only some samples actually include uapi headers from usr/include.
Introduce CONFIG_HEADERS_INSTALL since 'depends on HEADERS_INSTALL' is
clearer than 'depends on !UML'. If this option is enabled, uapi headers
are installed before starting directory descending.
I added 'depends on HEADERS_INSTALL' to per-sample CONFIG options.
This allows UML to compile some samples.
$ make ARCH=um allmodconfig samples/
[ snip ]
CC [M] samples/configfs/configfs_sample.o
CC [M] samples/kfifo/bytestream-example.o
CC [M] samples/kfifo/dma-example.o
CC [M] samples/kfifo/inttype-example.o
CC [M] samples/kfifo/record-example.o
CC [M] samples/kobject/kobject-example.o
CC [M] samples/kobject/kset-example.o
CC [M] samples/trace_events/trace-events-sample.o
CC [M] samples/trace_printk/trace-printk.o
AR samples/vfio-mdev/built-in.a
AR samples/built-in.a
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>