qemuv8: rust.exp: set timeout to 10 seconds

There is no timeout specified in rust.exp. This makes the tests
unreliable, because depending on which tests have been run before, the
$timeout global variable may have different values. For example, it is
set to 900 by qemu-check.exp (the main file), but may be overriden by
trusted-keys.exp to 5 seconds. That's not enough in some cases, causing
the following error in optee_os CI:

 2024-01-19T11:58:23.5778720Z Running signature_verification-rs...
 2024-01-19T11:58:28.3431817Z !!! Timeout: Test failed

Signed-off-by: Jerome Forissier <jerome.forissier@linaro.org>
Acked-by: Etienne Carriere <etienne.carriere@foss.st.com>
Acked-by: Jens Wiklander <jens.wiklander@linaro.org>
diff --git a/rust.exp b/rust.exp
index a41058a..f683b63 100644
--- a/rust.exp
+++ b/rust.exp
@@ -4,6 +4,8 @@
 # success, >0 for error.
 #
 
+set timeout 10
+
 info "Test Rust example applications:\n"
 info "Running acipher-rs...\n"
 send -- "acipher-rs 256 teststring\r"