Fix GDB script

Author: vacantron

.ci/gdbstub-test.sh

@@ -5,9 +5,9 @@ set -e -u -o pipefail
 export PATH=`pwd`/toolchain/bin:$PATH
 
 GDB=
-prefixes=("${CROSS_COMPILE}" "riscv32-unknown-elf" "riscv-none-elf")
+prefixes=("${CROSS_COMPILE}" "riscv32-unknown-elf-" "riscv-none-elf-")
 for prefix in "${prefixes[@]}"; do
-    utility=${prefix}-gdb
+    utility=${prefix}gdb
     set +e # temporarily disable exit on error
     command -v "${utility}" &> /dev/null
     if [[ $? == 0 ]]; then