Standard library option `http_enable_ssl_key_log_file` has no effect

[ianprime0509]

Zig Version

0.16.0-dev.727+95242cc43

Steps to Reproduce and Observed Behavior

There is a standard library option http_enable_ssl_key_log_file whose stated purpose is to tell std.http.Client to respect the SSLKEYLOGFILE environment variable for capturing TLS secrets:

zig/lib/std/std.zig

Lines 168 to 171 in 958faa7

	/// This enables `std.http.Client` to log ssl secrets to the file specified by the SSLKEYLOGFILE
	/// env var. Creating such a log file allows other programs with access to that file to decrypt
	/// all `std.http.Client` traffic made by this program.
	http_enable_ssl_key_log_file: bool = @import("builtin").mode == .Debug,

It is enabled by default in debug mode.

In particular, consider a debug build of the Zig compiler itself, and the following command:

SSLKEYLOGFILE=$HOME/tmp/sslkeylog stage4/bin/zig fetch git+https://github.com/ianprime0509/zig-xml

Using Zig 0.16.0-dev.727+95242cc43, this command does not write anything to the specified key log file.

Expected Behavior

Using a debug build of Zig 0.14.1, the command above logs TLS secrets to the specified key log file. Either this behavior should be restored (it is very useful for debugging), or the standard library option should be removed. (Even if the option is removed, I would still argue for its inclusion at least in debug builds of the compiler to help debug package fetching logic)

Some notes:

• The option was introduced in de53e6e (part of std.crypto.tls: implement TLSv1.2 #21872)
• The option stopped being referenced/respected in 02908a2 (part of std: rework HTTP and TLS for new I/O API #24698)