fix(build): Set module build flags needed for darwin shared libraries

Makefile.am

@@ -56,7 +56,7 @@ endif
 $(MANUAL): $(FIGURES)
 
 BUILT_SOURCES_LUA = core/features.lua core/pathsetup.lua core/version.lua
-RUSILE_SOURCES = rusile/Cargo.toml rusile/src/lib.rs
+RUSILE_SOURCES = rusile/Cargo.toml rusile/src/lib.rs build-aux/module.rs
 
 bin_PROGRAMS = sile
 bin_SCRIPTS = sile-lua

build-aux/module.rs

@@ -0,0 +1,3 @@
+fn main() {
+    println!("cargo:rustc-link-arg=-Wl,-undefined,dynamic_lookup");
+}

rusile/Cargo.toml

@@ -9,6 +9,7 @@ authors.workspace = true
 homepage.workspace = true
 repository.workspace = true
 license.workspace = true
+build = "../build-aux/module.rs"
 
 [lib]
 crate-type = ["rlib", "cdylib", "staticlib"]