[libc] Revamp hdrgen command line and build integration (#121522)

This adds a new main command-line entry point for hdrgen, in the
new main.py.  This new interface is used for generating a header.
The old ways of invoking yaml_to_classes.py for other purposes
are left there for now, but `--e` is renamed to `--entry-point`
for consistency with the new CLI.

The YAML schema is expanded with the `header_template` key where
the corresponding `.h.def` file's path is given relative to where
the YAML file is found.  The build integration no longer gives
the `.h.def` path on the command line.  Instead, the script now
emits a depfile that's used by the cmake rules to track that.
The output file is always explicit in the script command line
rather than sometimes being derived from a directory path.

1 files changed, 1 insertions, 0 deletions

diff --git a/libc/include/assert.yaml b/libc/include/assert.yaml
index f740554488ed..1a3bdeda7e54 100644
--- a/libc/include/assert.yaml
+++ b/libc/include/assert.yaml
@@ -1,4 +1,5 @@
 header: assert.h
+header_template: assert.h.def
 macros: []
 types: []
 enums: []