Add limited sandbox capability to "make check"

== Rationale ==

r295380 introduced "make check" and consolidated means for running
test code in an attempt to simplify running tests. One could either
install files/libraries/programs and run "make check", or run "make check"
with an explicit CHECKDIR, e.g., `make check CHECKDIR=$(make -V.OBJDIR)``.

One criticism that was received is that "make check" should be run with
the intent of making dev->test->commit easier, which means that the target
audience's workflow should be developers. One developer pattern available
in other opensource projects is to run test code from a developer sandbox,
instead of installing to a system.

== Method ==

This approach is slightly different from the standard approach, in the sense
that it builds and installs into a deterministic directory under .OBJDIR (as I call it,
the "sandbox"), then runs "make check" against that. In the event the test
run is successful, the deterministic directory is removed to save space.

== Approach ==

bsd.lib.mk, bsd.prog.mk:

To support this functionality, a new variable `HAS_TESTS` is being added.

HAS_TESTS enables appropriate behavior with bsd.lib.mk and bsd.prog.mk, as
follows:
- Add "make check" as an available target from the directory.
- Pass down appropriate variables via ${TESTS_ENV}, i.e.,
  ${TESTS_LD_LIBRARY_PATH} and ${TESTS_PATH}.

One should add "HAS_TESTS" to directories containing tests in them, e.g. from
bin/sh/Makefile,

  HAS_TESTS=
  SUBDIR.${MK_TESTS}+= tests

HAS_TESTS doesn't automatically add the tests subdirectory for flexibility
reasons.

bsd.opts.mk, src.opts.mk:
- The knob ${MK_MAKE_CHECK_USE_SANDBOX} has been added, both to explicitly
  direct (internally) when to set a deterministic ${DESTDIR} and to also allow
  users to disable this behavior globally, i.e., via src.conf.
- MK_TESTS has been promoted from src.opts.mk to bsd.opts.mk to leverage
  syntactic sugar for having MK_TESTS be a dependency for
  MK_MAKE_CHECK_USE_SANDBOX, but to also ensure that src.opts.mk isn't required
  to use suite.test.mk (which is a dependency of bsd.test.mk).

suite.test.mk:
- beforecheck behavior (when MK_MAKE_CHECK_USE_SANDBOX is enabled) is modified
  from a no-op to:
-- Build.
-- Run "make hierarchy" on the sandbox dir.
-- Install the tests/files to the sandbox dir.
- aftercheck behavior (when MK_MAKE_CHECK_USE_SANDBOX is enabled) is modified
  from a no-op to:
-- Remove the sandbox dir.

Again, because the dependency order set in bsd.test.mk is
beforecheck -> check -> aftercheck, "make check" will not be run unless
"beforecheck" completes successfully, and "aftercheck" will not be run unless
"beforecheck" and "check" complete successfully.

== Caveats ==

- This target must either be run with MK_INSTALL_AS_USER or as root. Otherwise
  it will fail when running "make install" as the default user/group for many
  makefiles when calling INSTALL is root/wheel.
- This target must be run from a suitable top-level directory. For example,
  running tests from `tests/sys/fs/tmpfs` won't work, but `tests/sys/fs` will,
  because `tests/sys/fs/tmpfs` relies on files installed by `tests/sys/fs`.
- Running MK_INSTALL_AS_USER may introduce determinism issues. However, using
  it could identify deficiences in tests in terms of needing to be run as
  root, which are not properly articulated in the test requirements.
- The doesn't negate the need for running "make installworld" and
  "make checkworld", etc. Again, this just is intended to simplify the
  dev->test->commit workflow.

== Cleanup done ==
- CHECKDIR is removed; one can use "MK_MAKE_CHECK_USE_SANDBOX=no" to enable
  "legacy" (r295380) behavior.

MFC after:	2 months
Relnotes:	yes (CHECKDIR removed; "make check" behavior changed)
Requested by:	jhb
Reviewed by:	arch (silence), testing (silence)
Differential Revision:	D11905

1 files changed, 10 insertions, 0 deletions

diff --git a/tools/build/options/WITHOUT_MAKE_CHECK_USE_SANDBOX b/tools/build/options/WITHOUT_MAKE_CHECK_USE_SANDBOX
new file mode 100644
index 000000000000..9ab94f04f36e
--- /dev/null
+++ b/tools/build/options/WITHOUT_MAKE_CHECK_USE_SANDBOX
@@ -0,0 +1,10 @@
+.\" $FreeBSD$
+Set to not execute
+.Dq Li "make check"
+in limited sandbox mode.
+This option should be paired with
+.Va WITH_INSTALL_AS_USER
+if executed as an unprivileged user.
+See
+.Xr tests 7
+for more details.