Fix detecting required libraries with cargo 1.71 and workspaces

`cargo new` now seems to write `version.workspace` into the
Cargo.toml, which we don't want, since our crate should not belong
to the workspace.

Instead of relying on the generated Cargo.toml we overwrite the generated
Cargo.toml with our own. This should prevent similar future issues.

cmake/FindRust.cmake

@@ -145,8 +145,14 @@ function(_corrosion_determine_libs_new target_triple out_libs)
         message(DEBUG "Determining required link libraries: failed to create test library: ${cargo_new_result}")
         return()
     endif()
-    file(APPEND "${CMAKE_BINARY_DIR}/corrosion/required_libs/Cargo.toml"
-            "[lib]\ncrate-type=[\"staticlib\"]\n[workspace]")
+    # Cargo new may create a Cargo.toml which attempts to reference keys from an outside workspace,
+    # but our package is not part of that workspace, so we need to overwrite the Cargo.toml with
+    # our own.
+    set(manifest_path "${CMAKE_BINARY_DIR}/corrosion/required_libs/Cargo.toml")
+    set(manifest "[package]\nname = \"required_libs\"\nedition = \"2018\"\nversion = \"0.1.0\"\n")
+    string(APPEND manifest "\n[lib]\ncrate-type=[\"staticlib\"]\n[workspace]\n")
+    file(WRITE "${manifest_path}" "${manifest}")
+
     execute_process(
         COMMAND ${CMAKE_COMMAND} -E env
             "CARGO_BUILD_RUSTC=${Rust_COMPILER_CACHED}"

test/workspace/workspace/Cargo.toml

@@ -1,2 +1,5 @@
 [workspace]
 members=["member1", "member2", "member3"]
+
+[workspace.package]
+version = "0.1.0"