MFC r288179:

Fix running make in src directories without a Makefile giving confusing
errors.

MFC:

Merge r276846: Add infrastructure to build dtb files from dts files.

MFC r268300 r268541 r268544 r268565 r269775 r269838 r269839 r269840
r269842 r269844 r269899:

BSD make support for generating and compiling USDT DTrace probes.

MFC refactoring of the *.test.mk files.

- r263161 Make bsd.test.mk the only public mk fragment for the building of tests.
- r263172 Move FreeBSD Test Suite-specific code to a suite.test.mk file.
- r263204 Add some documentation for bsd.test.mk.
- r263217 Document support for TAP-compliant Perl test programs.

This is "make tinderbox" clean.

Set up the /usr/tests hierarchy.

This is a MFC of the following into stable/10:
- r257097 Set up the /usr/tests hierarchy.
- r257098 Add missing WITHOUTTESTS file.
- r257100 Add a tests(7) manual page.
- r257105 Disable WITHTESTS= for now.
- r257848 Fix buildworld when WITHTESTS is enabled.
- r257850 Subsume the functionality of MKATF into MKTESTS.
- r257851 Handle the removal of the test suite when WITHOUTTESTS=yes.
- r257852 Install category Kyuafiles from their category directories.
- r258232 Install BSD.tests.mtree when MKTESTS is yes.

Note that building with WITH_TESTS is still broken at this point (and
hence why WITHOUT_TESTS is the set as the default). Subsequent pullups
will fix the remaining issues.

Split and extend bsd.test.mk into {atf,plain,tap}.test.mk.

This is a MFC of:

- r256761 Clearly split the logic to build ATF and plain tests apart.
- r256762 Add the automatic generation of Atffile files.
- r256763 Add the automatic generation of Kyuafile files.
- r256764 Plug atf-run into the 'test' target.
- r256765 Plug kyua into the 'test' target.
- r257096 Move the TESTSBASE definition to bsd.own.mk.
- r257099 Add missing plain.test.mk.
- r258297 Remove registration of C++ test programs into PROGS.
- r258298 Fix the build of plain test programs.
- r258551 Install plain.test.mk.
- r259208 Add tap.test.mk.

Approved by: rpaulo (mentor)

MFC:

Merge r276846: Add infrastructure to build dtb files from dts files.

MFC r268300 r268541 r268544 r268565 r269775 r269838 r269839 r269840
r269842 r269844 r269899:

BSD make support for generating and compiling USDT DTrace probes.

MFC refactoring of the *.test.mk files.

- r263161 Make bsd.test.mk the only public mk fragment for the building of tests.
- r263172 Move FreeBSD Test Suite-specific code to a suite.test.mk file.
- r263204 Add some documentation for bsd.test.mk.
- r263217 Document support for TAP-compliant Perl test programs.

This is "make tinderbox" clean.

Set up the /usr/tests hierarchy.

This is a MFC of the following into stable/10:
- r257097 Set up the /usr/tests hierarchy.
- r257098 Add missing WITHOUTTESTS file.
- r257100 Add a tests(7) manual page.
- r257105 Disable WITHTESTS= for now.
- r257848 Fix buildworld when WITHTESTS is enabled.
- r257850 Subsume the functionality of MKATF into MKTESTS.
- r257851 Handle the removal of the test suite when WITHOUTTESTS=yes.
- r257852 Install category Kyuafiles from their category directories.
- r258232 Install BSD.tests.mtree when MKTESTS is yes.

Note that building with WITH_TESTS is still broken at this point (and
hence why WITHOUT_TESTS is the set as the default). Subsequent pullups
will fix the remaining issues.

Split and extend bsd.test.mk into {atf,plain,tap}.test.mk.

This is a MFC of:

- r256761 Clearly split the logic to build ATF and plain tests apart.
- r256762 Add the automatic generation of Atffile files.
- r256763 Add the automatic generation of Kyuafile files.
- r256764 Plug atf-run into the 'test' target.
- r256765 Plug kyua into the 'test' target.
- r257096 Move the TESTSBASE definition to bsd.own.mk.
- r257099 Add missing plain.test.mk.
- r258297 Remove registration of C++ test programs into PROGS.
- r258298 Fix the build of plain test programs.
- r258551 Install plain.test.mk.
- r259208 Add tap.test.mk.

Approved by: rpaulo (mentor)