https://github.com/rustls/rustls-ffi/pull/274
https://github.com/rustls/rustls-ffi/issues/220

From 1c1968a374b1e14551f32c360489185e9b6e4376 Mon Sep 17 00:00:00 2001
From: Luca Barbato <lu_zero@gentoo.org>
Date: Sat, 10 Dec 2022 12:00:41 +0100
Subject: [PATCH 1/2] Move the language configuration to cbindgen.toml

--- a/Makefile
+++ b/Makefile
@@ -33,7 +33,7 @@ target:
 	mkdir -p $@
 
 src/rustls.h: src/*.rs cbindgen.toml
-	cbindgen --lang C > $@
+	cbindgen > $@
 
 target/$(PROFILE)/librustls_ffi.a: src/*.rs Cargo.toml
 	RUSTFLAGS="-C metadata=rustls-ffi" cargo build $(CARGOFLAGS)
--- a/cbindgen.toml
+++ b/cbindgen.toml
@@ -1,4 +1,5 @@
 include_guard = "CRUSTLS_H"
+language = "C"
 
 usize_is_size_t = true
 

From 5d3e109bea0f3fe3d9080a5d5ca4e30c66d4e2e9 Mon Sep 17 00:00:00 2001
From: Luca Barbato <lu_zero@gentoo.org>
Date: Sat, 10 Dec 2022 12:29:23 +0100
Subject: [PATCH 2/2] Initial cargo-c support

--- a/Cargo.toml
+++ b/Cargo.toml
@@ -19,6 +19,7 @@ links = "rustls_ffi"
 # libraries.
 no_log_capture = []
 read_buf = ["rustls/read_buf"]
+capi = []
 
 [dependencies]
 # Keep in sync with RUSTLS_CRATE_VERSION in build.rs
@@ -33,3 +34,16 @@ num_enum = "0.5.4"
 [lib]
 name = "rustls_ffi"
 crate-type = ["lib", "staticlib"]
+
+
+[package.metadata.capi.header]
+name = "rustls"
+subdirectory = false
+
+[package.metadata.capi.library]
+name = "rustls"
+rustflags = "-Cmetadata=rustls-ffi"
+
+[package.metadata.capi.pkg_config]
+name = "rustls"
+filename = "rustls"