o allow env var MAKE_OBJDIR_CHECK_WRITABLE=no to skip writable
checks in InitObjdir. Explicit .OBJDIR target always allows
read-only directory.
o Fix building and unit-tests on non-BSD.
o More code cleanup and refactoring.
o More unit tests
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
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 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.
from ChangeLog:
(most of this by rillig@)
o lots of style and white-space cleanup
o lots more unit tests for variable modifiers
o simplified description of some functions
o str.c: refactor Str_Match
o var.c: debugging output for :@
constify VarModify parameter
fix :hash modifier on 16-bit platforms
remove unnecessary forward declarations
refactor ApplyModifier_SysV to have less indentation
simplify code for :E and :R
clean up code for :H and :T
refactor ApplyModifiers
* var.c: we need stdint.h on some platforms to get uint32_t
* unit-test/Makefile: we need to supress the specific error
for RE substitution error in modmisc, since it varies accross
different OS.
