When MAKEFLAGS is set in a makefile, reparse it immediately rather
than waiting until after all makefiles have been read and parsed.
This change doesn't actually fix the SV bug referenced because, even
though we do reparse MAKEFLAGS, we don't handle the -r or -R options
immediately. Doing this will require more effort.
* NEWS: Announce the change.
* src/makeint.h: Publish reset_switches() and decode_env_switches()
from main.c
* src/main.c (main): Don't call construct_include_path(); it will be
invoked decode_switches().
Preserve the old values of builtin_rules, builtin_variables, and
job_slots before we read makefiles since they can be changed now.
(reset_switches): Publish (remove static). Set the initial value of
the stringlist list to NULL.
(decode_switches): Call construct_include_path() after decoding.
(decode_env_switches): Publish (remove static).
(define_makeflags): Set the MAKEFLAGS variable for special handling.
* src/read.c (eval_makefile): Check for empty include_directories.
(construct_include_path): Clear any old value of .INCLUDE_DIRS before
appending new values. Free the previous include_directories.
* src/variable.c (lookup_special_var): When MAKEFLAGS is set, first
reset the switches then re-parse the variable.
* tests/run_make_tests.pl: Memo-ize some default variable values.
* tests/scripts/options/dash-r: Create tests for setting -r and -R.
* tests/scripts/variables/MAKEFLAGS: Test that resetting -I from
within the makefile takes effect immediately.
Accept a "-" directory value to the -I option to clear the set of
directories to be searched up to that point, including the default
directories.
* NEWS: Announce the change.
* doc/make.texi (Summary of Options): Add documentation.
* src/read.c (construct_include_path): Check for '-' and if found,
clear the list of directories to be searched.
* tests/scripts/options/dash-I: Add tests for -I-.
* tests/scripts/variables/INCLUDE_DIRS: Add tests for -I-.
