have haskell_repl output absolute paths or paths relative to a different folder than the workspace one

[teto]

Is your feature request related to a problem? Please describe.
This may be more of a bazel issue: I would like bazel to write paths relative to a different folder than the workspace root.

Specifically, calling

	bazel build "//hie_bios" \
	--output_groups=hie_bios \
	--experimental_show_artifacts \

defined by

load("@rules_haskell//haskell:defs.bzl", "haskell_repl")

# See https://api.haskell.build/haskell/defs.html#haskell_repl
haskell_repl(
    name = "hie_bios",
    collect_data = False,
    deps = {deps},
    experimental_from_source = {deps},
    # Required because we might depend on tests, and bazel only allows
    # 'testonly' targets to depend on tests
    testonly = True,
)

returns

-package-db
bazel-out/k8-fastbuild/bin/external/hackage/lrucaching-0.3.3/_install/lrucaching-0.3.3.conf.d
-package-db
bazel-out/k8-fastbuild/bin/external/hackage/haskell-lexer-1.1/_install/haskell-lexer-1.1.conf.d
-package-db
bazel-out/k8-fastbuild/bin/external/hackage/pretty-show-1.10/_install/pretty-show-1.10.conf.d
-package-db
bazel-out/k8-fastbuild/bin/external/hackage/unbounded-delays-0.1.1.0/_install/unbounded-delays-0.1.1.0.conf.d
-package-db
bazel-out/k8-fastbuild/bin/external/hackage/wcwidth-0.0.2/_install/wcwidth-0.0.2.conf.d
-package-db
bazel-out/k8-fastbuild/bin/external/hackage/tasty-1.2.3/_install/tasty-1.2.3.conf.d
-package-db
bazel-out/k8-fastbuild/bin/external/hackage/tasty-hunit-0.10.0.2/_install/tasty-hunit-0.10.0.2.conf.d
-pgma
bazel-out/k8-fastbuild/bin/external/rules_haskell/haskell/cc_wrapper-python
-pgmc
bazel-out/k8-fastbuild/bin/external/rules_haskell/haskell/cc_wrapper-python
-pgml
bazel-out/k8-fastbuild/bin/external/rules_haskell/haskell/cc_wrapper-python
-pgmP
bazel-out/k8-fastbuild/bin/external/rules_haskell/haskell/cc_wrapper-python -E -undef -traditional
-optc-fno-stack-protector
-fdiagnostics-color=always
-freduction-depth=0
-fwrite-ide-info
...

that I save in a module.flags file.

I would like to prefix the paths bazel-out/k8-fastbuild/bin/external/rules_haskell/haskell/ with ../.. for instance to get ../../bazel-out/k8-fastbuild/bin/external/rules_haskell/haskell/ instead. Or alternativatel absolute paths should work too.

Additional context
While trying to write a multicradle hie.yaml (see #1386), I realized that local hie.yaml files override the hie.yaml in the parent directory (haskell/hie-bios#250 (comment)). I liked the idea and went on with it so I have a:
BAZEL_WORKSPACE/subproject/hie.yaml that reads flags from BAZEL_WORKSPACE/module.flags . The problem is ghcide interprets paths from the hie.yaml directory so it looks for
BAZEL_WORKSPACE/subproject/bazel-out/k8-fastbuild/bin/external/hackage/lrucaching-0.3.3/_install/lrucaching-0.3.3.conf.d instead of BAZEL_WORKSPACE/bazel-out/k8-fastbuild/bin/external/hackage/lrucaching-0.3.3/_install/lrucaching-0.3.3.conf.d.
I've tried adding symlinks to bazel-out in BAZEL_WORKSPACE/subproject and itkinda fixed it, only to create infinite loops later that confuse both bazel and ghcide.

[teto]

btw I tried patching rules_haskell to get this behavior (just to try) and I could check my changes were taken into account but I couldn't see the output of my print statements in haskell/repl.bzl if you have any tip :)

[aherrmann]

This was addressed in #1531. @teto feel free to re-open if you feel something is still missing.

[teto]

thanks for everyone's work.