[gcc r15-8273] rust: force cargo to build offline

[Arthur Cohen]

https://gcc.gnu.org/g:d4fe08c2d4725c6b6024c08b330a7e8e9496c7c5

commit r15-8273-gd4fe08c2d4725c6b6024c08b330a7e8e9496c7c5
Author: Marc Poulhiès <dkm@kataplop.net>
Date:   Mon Mar 17 19:23:50 2025 +0100

    rust: force cargo to build offline
    
    gcc/rust/Changelog:
            PR rust/119333
    
            * Make-lang.in: Force offline mode for cargo
    
    Signed-off-by: Marc Poulhiès <dkm@kataplop.net>

Diff:
---
 gcc/rust/Make-lang.in | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/gcc/rust/Make-lang.in b/gcc/rust/Make-lang.in
index efa630927fab..c892fa3091e3 100644
--- a/gcc/rust/Make-lang.in
+++ b/gcc/rust/Make-lang.in
@@ -503,5 +503,5 @@ rust/%.o: rust/metadata/%.cc
 rust/libffi_polonius.a: \
 	rust/checks/errors/borrowck/ffi-polonius/Cargo.toml \
 	$(wildcard $(srcdir)/rust/checks/errors/borrowck/ffi-polonius/src/*)
-	cargo build --manifest-path $(srcdir)/rust/checks/errors/borrowck/ffi-polonius/Cargo.toml --release --target-dir rust/ffi-polonius
+	cd $(srcdir)/rust/checks/errors/borrowck/ffi-polonius/ && cargo build --offline --release --target-dir $(objdir)/rust/ffi-polonius
 	cp rust/ffi-polonius/release/libffi_polonius.a rust/libffi_polonius.a