Merge bitcoin-core/secp256k1#1660: ci: Fix exiting from ci.sh on error

d87c3bc58f ci: Fix exiting from ci.sh on error (Tim Ruffing)

Pull request description:

  Fixes the following bash error when make fails:
      ./ci/ci.sh: line 100: return: can only `return' from a function or
      sourced script

ACKs for top commit:
  hebasto:
    ACK d87c3bc58f

Tree-SHA512: 5ecd0f550f7659cc41b403fdb7d5d3d37d1a167d585cca02b0aca209c8b9592bb3067cf11aeb80775666e7232f31bf05cf1bb97fec8c67f3bc5fe2243ddbbcfa

ci/ci.sh

@@ -94,10 +94,10 @@ if [ $build_exit_code -ne 0 ]; then
         *snapshot*)
             # Ignore internal compiler errors in gcc-snapshot and clang-snapshot
             grep -e "internal compiler error:" -e "PLEASE submit a bug report" make.log
-            return $?;
+            exit $?
             ;;
         *)
-            return 1;
+            exit 1
             ;;
     esac
 fi