Support building libninja-re2c.a on configure.py

[ken-matsui]

configure.py currently builds only libninja.a, but we also want the libninja-re2c.a like CMakeLists.txt does:

ninja/CMakeLists.txt

Lines 47 to 50 in 55f5451

	add_library(libninja-re2c OBJECT ${PROJECT_BINARY_DIR}/depfile_parser.cc ${PROJECT_BINARY_DIR}/lexer.cc)
	else()
	message(WARNING "re2c was not found; changes to src/*.in.cc will not affect your build.")
	add_library(libninja-re2c OBJECT src/depfile_parser.cc src/lexer.cc)

[ken-matsui]

Hi @jonesmz,

The configure.py is currently used in both Homebrew and MacPorts (and might other sources), so I would say deleting the script would bring a big breaking change.

Thus, if this breaking change is acceptable, I think the script should be removed and I am more in favor of that.

[hadrielk]

Fedora and others use it too, in their RPM specs.

[ken-matsui]

Ah, then this PR should have the least impact, IMO.

[ken-matsui]

Yes, ideally, it would be great, and I would agree with you if I were a maintainer without historical background knowledge. Could you please open a PR that removes configure.py rather than updating this PR? Either yours or mine will be merged by maintainers.