tree 183724a6dcbc2d1c6b581eb893bdc89d8e93db95
parent 7e37c91cf342499b05015ee3bdc33a6755f98211
author Petr Hosek <phosek@google.com> 1594847456 -0700
committer Copybara-Service <copybara-worker@google.com> 1620587960 -0700

[libc++] Support per-target __config_site in per-target runtime build

When using the per-target runtime build, it may be desirable to have
different __config_site headers for each target where all targets cannot
share a single configuration.

The layout used for libc++ headers after this change is:

```
include/
  c++/
    v1/
      <libc++ headers except for __config_site>
  <target1>/
    c++/
      v1/
        __config_site
  <target2>/
    c++/
      v1/
        __config_site
  <other targets>
```

This is the most optimal layout since it avoids duplication, the only
headers that's per-target is __config_site, all other headers are
shared across targets. This also means that we no need two
-isystem flags: one for the target-agnostic headers and one for
the target specific headers.

Differential Revision: https://reviews.llvm.org/D89013

GitOrigin-RevId: ea12d779bc238c387511fe7462020f4ecf4a8246