Use $CARGO instead of cargo in test scripts

test_crates/catch_std_exception/check.sh

@@ -1,7 +1,7 @@
 #!/usr/bin/env bash
 set -o pipefail
 trap "rm -f run.log" EXIT
-cargo run --release $BUILD_STD 2>&1 | tee run.log
+${CARGO:-cargo} run --release $BUILD_STD 2>&1 | tee run.log
 if [ $? -ne 134 ]; then
     echo process is not aborted
     exit 1

test_crates/std_catch_exception/check.sh

@@ -1,7 +1,7 @@
 #!/usr/bin/env bash
 set -o pipefail
 trap "rm -f run.log" EXIT
-cargo run --release $BUILD_STD 2>&1 | tee run.log
+${CARGO:-cargo} run --release $BUILD_STD 2>&1 | tee run.log
 if [ $? -ne 134 ]; then
     echo process is not aborted
     exit 1

test_crates/throw_and_catch/check.sh

@@ -1,7 +1,7 @@
 #!/usr/bin/env bash
 set -o pipefail
 trap "rm -f run.log" EXIT
-cargo run --release $BUILD_STD 2>&1 | tee run.log
+${CARGO:-cargo} run --release $BUILD_STD 2>&1 | tee run.log
 if [ $? -ne 134 ]; then
     echo process is not aborted
     exit 1