Optionally unset a linkopt

[sluongng]

My use case is that we are currently doing this

common --enable_platform_specific_config=true

...

common:macos --linkopt="-Wl,-no_warn_duplicate_libraries"
common:macos --host_linkopt="-Wl,-no_warn_duplicate_libraries"

to silent the Xcode 15 warning about duplicated -lm flags.

However, on MacOS, we could optionally enable --config=remote to build remotely on Linux RBE.
And our linker on Linux does not like to have those flags passed to it.

/usr/bin/ld.gold: fatal error: -pie and -static are incompatible
collect2: error: ld returned 1 exit status
compilepkg: error running subcommand /usr/bin/gcc: exit status 1

(ignore the irrelevant error message, it's mostly just ld.gold linker not recognizing the flag above)

So ideally, I am looking for a way to set the above flags by default but wipe them when --config=remote is enabled.
I am looking into platform_mapping right now as a potential solution, but the API is deemed to be unstable and the feature will go away in the future.

A simple solution for this would be to be able to set a default --linkopt in .bazelrc for macOS builds, but to have the ability to unset it when needed (i.e. when RBE is manually enabled with --config=remote).

[sluongng]

Ended using platform_mapping to solve my problem https://github.com/buildbuddy-io/buildbuddy/pull/5680/files

Would love to hear suggestions for alternatives.

[keith]

note that for this specific problem we solve this in the toolchain now with a feature, so you could use build:remote --features=-no_warn_duplicate_libraries

[sluongng]

cc: @brentleyjones

I think this is only available in apple_support cc toolchain, which we recently disabled by default? 🤔

[brentleyjones]

Correct. We aren't using the apple support toolchain.