Implement --emit-symbol-list

The test recreates the motivating situation in the issue, where there
are two bindgen invocations, and we want them to build upon each other,
not duplicate each other.

Fix #3326

Author: Ericson2314

Cargo.lock

@@ -42,6 +42,8 @@ quickcheck = "1.0"
 quote = { version = "1", default-features = false }
 regex = { version = "1.5.3", default-features = false }
 rustc-hash = "2.1.0"
+serde = { version = "1.0", features = ["derive"] }
+serde_json = "1.0"
 shlex = "1"
 similar = "2.2.1"
 syn = "2.0"

Cargo.toml

@@ -13,6 +13,8 @@ owo-colors.workspace = true
 prettyplease = { workspace = true, features = ["verbatim"] }
 proc-macro2.workspace = true
 regex.workspace = true
+serde.workspace = true
+serde_json.workspace = true
 shlex.workspace = true
 similar = { workspace = true, features = ["inline"] }
 syn.workspace = true

bindgen-tests/Cargo.toml

@@ -0,0 +1,19 @@
+{
+  "types": [
+    "foo_int_t",
+    "int",
+    "foo_struct",
+    "int",
+    "float",
+    "_bindgen_ty_id_9",
+    "int",
+    "void",
+    "int"
+  ],
+  "functions": [
+    "foo_function"
+  ],
+  "vars": [
+    "foo_global_var"
+  ]
+}

bindgen-tests/tests/expectations/tests/emit-symbol-list-bar.rs

@@ -0,0 +1,11 @@
+type my_int_t
+type int
+type my_struct
+type int
+type float
+type _bindgen_ty_id_9
+type int
+type void
+function my_function
+type int
+var my_global_var

bindgen-tests/tests/expectations/tests/emit-symbol-list-foo.rs

@@ -0,0 +1,15 @@
+// Dependent library header (like "bar" in the issue)
+// bar depends on foo
+
+#include "emit-symbol-list-foo.h"
+
+typedef foo_int_t bar_int_t;
+
+struct bar_struct {
+    struct foo_struct foo;
+    int z;
+};
+
+void bar_function(struct foo_struct* arg, struct bar_struct* arg2);
+
+extern int bar_global_var;

bindgen-tests/tests/expectations/tests/emit-symbol-list-foo.symbols

@@ -0,0 +1,12 @@
+// Base library header (like "foo" in the issue)
+
+typedef int foo_int_t;
+
+struct foo_struct {
+    int x;
+    float y;
+};
+
+void foo_function(int arg);
+
+extern int foo_global_var;