configure: have --enable-debug set -C debug-assertions=on so debug!() works again

[codyps]

configure: have --enable-debug set -C debug-assertions=on so debug!() works again

[rust-highfive]

r? @alexcrichton

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[emberian]

@bors r+ fbc10c3 rollup

[Manishearth]

This might be breaking tests

I get the following error in the rollup:

command: x86_64-unknown-linux-gnu/stage1/bin/rustc /opt/rust/src/test/run-pass/regions-nullary-variant.rs -L x86_64-unknown-linux-gnu/test/run-pass/ --target=x86_64-unknown-linux-gnu -L x86_64-unknown-linux-gnu/test/run-pass/regions-nullary-variant.stage1-x86_64-unknown-linux-gnulibaux -C prefer-dynamic -o x86_64-unknown-linux-gnu/test/run-pass/regions-nullary-variant.stage1-x86_64-unknown-linux-gnu --cfg rtopt --cfg debug =on -O -L x86_64-unknown-linux-gnu/rt
stdout:
------------------------------------------

------------------------------------------
stderr:
------------------------------------------
error: multiple input filenames provided

------------------------------------------

Note the -cfg debug =on, this seems to be happening for all of the rpass tests. Could you run make check-stage1-rpass and see if it's your PR causing the issue?

[pnkfelix]

Yes, it is colliding with the logic in this line:
https://github.com/jmesmon/rust/blob/fix-debug/mk/tests.mk#L593

CTEST_RUSTC_FLAGS := $$(subst -C debug-assertions,,$$(CFG_RUSTC_FLAGS))

[pnkfelix]

(an easy hack fix would be to put in two subst invocations there; the inner one would replace all -C debug-assertions=on with the empty string, and then the outer one would be the one we currently do.)

[codyps]

I've added a commit that does the quick hack @pnkfelix suggested.
Actually removing all the possible variants of debug-assertions probably requires the use of $(shell sed ...) in some form.

[alexcrichton]

@bors: r+ 100e1a9