Zig to wasm supports tiny modules.

add.wat

(module
  (type (;0;) (func (param i32 i32) (result i32)))
  (func $add (type 0) (param i32 i32) (result i32)
    local.get 1
    local.get 0
    i32.add)
  (table (;0;) 1 1 funcref)
  (memory (;0;) 2)
  (global (;0;) (mut i32) (i32.const 66560))
  (export "memory" (memory 0))
  (export "add" (func $add)))

add.zig

export fn add(a: i32, b: i32) i32 {
    return a + b;
}

compile.log

$ zig build-lib add.zig -target wasm32-freestanding --release-small --strip --single-threaded
$ wasm2wat add.wasm