Fix target naming to follow symbolic macro naming requirements

[reutermj]

Any target produced by a symbolic macro must start with the name of the macro. cc_toolchain produces two sets of targets prefixed with _ instead of the name. This change drops the _ prefix from the targets produced by cc_toolchain to enable its use in symbolic macros.

example error:

ERROR: /home/mark/.cache/bazel/_bazel_mark/5979f8eda1b07b2dab85fbe51f06c597/external/toolchains_cc++cxx_toolchains+toolchains_cc_default_toolchain/BUILD:3:18: in cc_toolchain_config rule @@toolchains_cc++cxx_toolchains+toolchains_cc_default_toolchain//:_toolchains_cc_default_toolchain_cc_toolchain_config: Target @@toolchains_cc++cxx_toolchains+toolchains_cc_default_toolchain//:_toolchains_cc_default_toolchain_cc_toolchain_config declared in symbolic macro 'toolchains_cc_default_toolchain' violates macro naming rules and cannot be built. Name must be the same as the macro's name, or the macro's name followed by '_' (recommended), '-', or '.', and a non-empty string.

fix verified with working toolchain: https://github.com/reutermj/toolchains_cc/tree/backup-gcc

[armandomontanez]

This target is intended to be private so we don't have other folks rely on the intermediate target, so it's named with a _{name} prefix which is part of the bzl style guide. Is there a flag to turn this check off until either the check or style guide are improved?

[reutermj]

There's nothing blocking me on my end. I can (and currently do) just use a legacy macro in the meantime which doesn't have the naming check. Yeah the style guide and the symbolic macro requirements aren't in agreement:

Have their names prefixed by <name> or _<name>. For example, using name = '%s_bar' % (name).

https://bazel.build/rules/bzl-style#macros

The names of any targets or submacros created by a symbolic macro must either match the macro's name parameter or must be prefixed by name followed by _ (preferred), . or -.

https://bazel.build/extending/macros#naming

[reutermj]

@armandomontanez the style guide has been updated as of: bazelbuild/bazel#27005

Can we get this revisited?

[dzbarsky]

This will be fixed as a side effect of #555