cbindgen: Fix rare issue with cbindgen failing to find cargo

PATH may be different at build time, so cargo might not be in
PATH, which would cause cbindgen to fail.
We point cbindgen to the correct CARGO executable explicitly instead.

Author: jschwe

cmake/Corrosion.cmake

@@ -2137,6 +2137,8 @@ function(corrosion_experimental_cbindgen)
         COMMAND
         "${CMAKE_COMMAND}" -E env
             TARGET="${cbindgen_target_triple}"
+            # cbindgen invokes cargo-metadata and checks the CARGO environment variable
+            CARGO="${_CORROSION_CARGO}"
             "${cbindgen}"
                     --output "${generated_header}"
                     --crate "${rust_cargo_package}"