chore: import upstream snapshot with attribution

examples/c-interop/src/main.0

@@ -0,0 +1,5 @@
+extern c "examples/c-interop/vendor/include/mathshim.h" as math
+
+pub fn main(world: World) -> Void raises {
+    check world.out.write("c interop metadata ok\n")
+}

examples/c-interop/vendor/include/mathshim.h

@@ -0,0 +1,3 @@
+#define MATHSHIM_VERSION 1
+
+int mathshim_add(int a, int b);

examples/c-interop/vendor/lib/libmathshim.a

@@ -0,0 +1 @@
+placeholder archive for manifest validation

examples/c-interop/zero.toml

@@ -0,0 +1,15 @@
+[package]
+name = "c-interop"
+version = "0.1.0"
+
+[targets.cli]
+kind = "exe"
+main = "src/main.0"
+
+[c.libs.math]
+headers = ["vendor/include/mathshim.h"]
+include = ["vendor/include"]
+lib = ["vendor/lib/libmathshim.a"]
+link = ["mathshim"]
+mode = "static"
+pkg_config = "mathshim"