incompatible_remove_host_cc_options: Remove host exclusive C++ options

[hlopko]

Flag: --incompatible_remove_host_specific_cc_options
Available since: todo
Will be flipped in: todo
Tracking issue: #6516

Motivation

With the move of C++ rules to use platforms/toolchains (tracked in #6516), we are removing host specific logic. Platforms don't guarantee existence of separate host toolchain, in which case having both --host_copt and --copt is confusing, and it can happen that there will be multiple execution platforms, which currently don't have a --copt flag. My research shows that these Bazel options are actually mostly unused, so instead of coming up with non-trivial solution, we will remove these options.

There are already mechanisms how to alter the command lines - crosstool features, and/or copts and linkopts attributes on rules. If this is not enough, we can investigate other options. Feel free to start the conversation on this issue.

Migration

Affected options:

• --host_copt
• --host_cxxopt
• --host_conlyopt
• --host_linkopt
• --host_grte_top

These will be removed. Migration options are using rule attributes, and crosstool features.

[hlopko]

CC @katre

[hlopko]

Closing - this is no longer needed for C++ rules to migrate to platforms.