bpo-40424: allow makexp_aix to manage parallel build requests

[aixtools]

Make the build utility makexp_aix able to deal with parallel build make (-jNN)
Patch by M. Felt.

https://bugs.python.org/issue40424

[aixtools]

p.s. I did not bother with a NEWS blurb - not really related to Python (sic)

[aixtools]

OOps - had not seen skip news today - so added something.

Shall I delete it?

[aixtools]

Just thought I'd mention - most of the bot failures, such as: https://buildbot.python.org/all/#builders/227/builds/1150 are caused because makexp_aix was not written (in 1998 and 1999) for parallel processing.

This leads to:

...
./install-sh -c -m 644 ./Tools/gdb/libpython.py python-gdb.py
gcc -pthread -c -Wno-unused-result -Wsign-compare -g -Og -Wall    -std=c99 -Wextra -Wno-unused-result -Wno-unused-parameter -Wno-missing-field-initializers -Werror=implicit-function-declaration -fvisibility=hidden  -I./Include/internal  -I. -I./Include    -DPy_BUILD_CORE -o Programs/_testembed.o ./Programs/_testembed.c
sed -e "s,@EXENAME@,/home/shager/cpython-buildarea/3.x.edelsohn-aix-ppc64/build/target/bin/python3.10d," < ./Misc/python-config.in >python-config.py
LC_ALL=C sed -e 's,\$(\([A-Za-z0-9_]*\)),\$\{\1\},g' < Misc/python-config.sh >python-config
gcc -pthread -c -Wno-unused-result -Wsign-compare -g -Og -Wall    -std=c99 -Wextra -Wno-unused-result -Wno-unused-parameter -Wno-missing-field-initializers -Werror=implicit-function-declaration -fvisibility=hidden  -I./Include/internal  -I. -I./Include    -DPy_BUILD_CORE \
      -DGITVERSION="\"`LC_ALL=C git --git-dir ./.git rev-parse --short HEAD`\"" \
      -DGITTAG="\"`LC_ALL=C git --git-dir ./.git describe --all --always --dirty`\"" \
      -DGITBRANCH="\"`LC_ALL=C git --git-dir ./.git name-rev --name-only HEAD`\"" \
      -o Modules/getbuildinfo.o ./Modules/getbuildinfo.c
rm -f libpython3.10d.a
ar rcs libpython3.10d.a Modules/getbuildinfo.o Parser/acceler.o Parser/grammar1.o Parser/listnode.o Parser/node.o Parser/parser.o Parser/token.o  Parser/pegen/pegen.o Parser/pegen/parse.o Parser/pegen/parse_string.o Parser/pegen/peg_api.o Parser/myreadline.o Parser/parsetok.o Parser/tokenizer.o Objects/abstract.o Objects/accu.o Objects/boolobject.o Objects/bytes_methods.o Objects/bytearrayobject.o Objects/bytesobject.o Objects/call.o Objects/capsule.o Objects/cellobject.o Objects/classobject.o Objects/codeobject.o Objects/complexobject.o Objects/descrobject.o Objects/enumobject.o Objects/exceptions.o Objects/genericaliasobject.o Objects/genobject.o Objects/fileobject.o Objects/floatobject.o Objects/frameobject.o Objects/funcobject.o Objects/interpreteridobject.o Objects/iterobject.o Objects/listobject.o Objects/longobject.o Objects/dictobject.o Objects/odictobject.o Objects/memoryobject.o Objects/methodobject.o Objects/moduleobject.o Objects/namespaceobject.o Objects/object.o Objects/obmalloc.o Objects/picklebufobject.o Objects/rangeobject.o Objects/setobject.o Objects/sliceobject.o Objects/structseq.o Objects/tupleobject.o Objects/typeobject.o Objects/unicodeobject.o Objects/unicodectype.o Objects/weakrefobject.o Python/_warnings.o Python/Python-ast.o Python/asdl.o Python/ast.o Python/ast_opt.o Python/ast_unparse.o Python/bltinmodule.o Python/ceval.o Python/codecs.o Python/compile.o Python/context.o Python/dynamic_annotations.o Python/errors.o Python/frozenmain.o Python/future.o Python/getargs.o Python/getcompiler.o Python/getcopyright.o Python/getplatform.o Python/getversion.o Python/graminit.o Python/hamt.o Python/hashtable.o Python/import.o Python/importdl.o Python/initconfig.o Python/marshal.o Python/modsupport.o Python/mysnprintf.o Python/mystrtoul.o Python/pathconfig.o Python/peephole.o Python/preconfig.o Python/pyarena.o Python/pyctype.o Python/pyfpe.o Python/pyhash.o Python/pylifecycle.o Python/pymath.o Python/pystate.o Python/pythonrun.o Python/pytime.o Python/bootstrap_hash.o Python/structmember.o Python/symtable.o Python/sysmodule.o Python/thread.o Python/traceback.o Python/getopt.o Python/pystrcmp.o Python/pystrtod.o Python/pystrhex.o Python/dtoa.o Python/formatter_unicode.o Python/fileutils.o Python/dynload_shlib.o    Modules/config.o Modules/getpath.o Modules/main.o Modules/gcmodule.o Modules/posixmodule.o  Modules/errnomodule.o  Modules/pwdmodule.o  Modules/_sre.o  Modules/_codecsmodule.o  Modules/_weakref.o  Modules/_functoolsmodule.o  Modules/_operator.o  Modules/_collectionsmodule.o  Modules/_abc.o  Modules/itertoolsmodule.o  Modules/atexitmodule.o  Modules/signalmodule.o  Modules/_stat.o  Modules/timemodule.o  Modules/_threadmodule.o  Modules/_localemodule.o  Modules/_iomodule.o Modules/iobase.o Modules/fileio.o Modules/bytesio.o Modules/bufferedio.o Modules/textio.o Modules/stringio.o  Modules/faulthandler.o  Modules/_tracemalloc.o  Modules/_peg_parser.o  Modules/symtablemodule.o  Modules/xxsubtype.o Python/frozen.o
./Modules/makexp_aix Modules/python.exp . libpython3.10d.a;  gcc -pthread     -Wl,-bE:Modules/python.exp -lld -o python Programs/python.o libpython3.10d.a -lintl -ldl  -lm   -lm 
./Modules/makexp_aix Modules/python.exp . libpython3.10d.a;  gcc -pthread     -Wl,-bE:Modules/python.exp -lld -o Programs/_testembed Programs/_testembed.o libpython3.10d.a -lintl -ldl  -lm   -lm 
ld: 0711-418 ERROR: Import or export file Modules/python.exp at line 2:
	A symbol name may only be followed by an export attribute
	or an address. The line is being ignored.
ld: 0711-415 WARNING: Symbol PyAST_Check is already exported.
ld: 0711-415 WARNING: Symbol PyAST_Compile is already exported.
...

Specifically, the lines:

./Modules/makexp_aix Modules/python.exp . libpython3.10d.a;  gcc -pthread     -Wl,-bE:Modules/python.exp -lld -o python Programs/python.o libpython3.10d.a -lintl -ldl  -lm   -lm 
./Modules/makexp_aix Modules/python.exp . libpython3.10d.a;  gcc -pthread     -Wl,-bE:Modules/python.exp -lld -o Programs/_testembed Programs/_testembed.o libpython3.10d.a -lintl -ldl  -lm   -lm 

cause the file Modules/python.exp to be created in parallel - and besides frequently causing a build crash - it is also causing about 22k lines of warnings of symbols already exported.

This PR is to minimize, if not eliminate, both issues.

Your consideration for a merge is appreciated.

[kadler]

LGTM but to be fair, I helped write it 😁

[aixtools]

Quite right. And a different form is already added, so closing.