add some conf packages

packages/conf-lld/conf-lld.1/opam

@@ -0,0 +1,18 @@
+opam-version: "2.0"
+maintainer: "Léo Andrès <[email protected]>"
+authors: "The LLVM team"
+homepage: "http://llvm.org"
+bug-reports: "https://llvm.org/bugs/"
+license: "MIT"
+build: [
+  ["wasm-ld" "-version"]
+]
+depends: [
+  "conf-bash" {build}
+]
+depexts: [
+  ["lld"] { os-family = "debian" }
+  ["llvm"] { os-family = "homebrew" }
+]
+synopsis: "Virtual package relying on lld installation"
+flags: conf

packages/conf-rust-llvm/conf-rust-llvm.1/opam

@@ -0,0 +1,17 @@
+opam-version: "2.0"
+maintainer: "Léo Andrès <[email protected]>"
+authors: "Léo Andrès <[email protected]>"
+homepage: "https://github.com/ocaml/opam-repository"
+bug-reports: "https://github.com/ocaml/opam-repository/issues"
+license: "MIT"
+build: [
+  ["which" "rust-lld"]
+]
+depends: [
+  "conf-bash" {build}
+]
+depexts: [
+  ["rust-llvm"] { os-family = "debian" }
+]
+synopsis: "Virtual package relying on an installation of the integration of Rust with LLVM tools."
+flags: conf

packages/conf-rust-wasm/conf-rust-wasm.1/opam

@@ -0,0 +1,18 @@
+opam-version: "2.0"
+maintainer: "Léo Andrès <[email protected]>"
+authors: "Léo Andrès <[email protected]>"
+homepage: "https://github.com/ocaml/opam-repository"
+bug-reports: "https://github.com/ocaml/opam-repository/issues"
+license: "MIT"
+build: [
+  ["sh" "-c" "rustc --print target-list | grep -q 'wasm32-unknown-unknown'" ]
+]
+depends: [
+  "conf-bash" {build}
+  "conf-rust" {build}
+]
+depexts: [
+  ["libstd-rust-dev-wasm32"] { os-family = "debian" }
+]
+synopsis: "Virtual package relying on an installation of standard Rust libraries including development files, needed to cross-compile Rust programs to the wasm32-unknown-unknown and wasm32-wasip1/wasm32-wasip2 targets"
+flags: conf