Merge bmake-20211212

commit '2935fe8237c83c1dcb113dd5335733263e68e6fd'

Merge bmake-20210206

Changes of interest

o unit-tests: use private TMPDIR to avoid errors from other users
o avoid strdup in mkTempFile
o always use vfork
o job.c: do not create empty shell files in jobs mode
reduce unnecessary calls to waitpid
o cond.c: fix debug output for comparison operators in conditionals

Update to bmake-20201101

Lots of new unit-tests increase code coverage.

Lots of refactoring, cleanup and simlpification to reduce
code size.

Fixes for Bug 223564 and 245807

Updates to dirdeps.mk and meta2deps.py

Update to bmake-20200902

Lots of code refactoring, simplification and cleanup.
Lots of new unit-tests providing much higher code coverage.
All courtesy of rillig at netbsd.

Other significant changes:

o new read-only variable .SHELL which provides the path of the shell
used to run scripts (as defined by the .SHELL target).

o variable parsing detects more errors.

o new debug option -dl: LINT mode, does the equivalent of := for all
variable assignments so that file and line number are reported for
variable parse errors.

Merge bmake 20151020