[tests] fix tests broken when directory 'tests/bts' has been introduced

src/plugins/e-acsl/gcc_bts.sh

src/plugins/e-acsl/gcc_runtime.sh

src/plugins/e-acsl/gcc_test.sh

src/plugins/e-acsl/tests/bts/bts1304.i

src/plugins/e-acsl/tests/bts/bts1307.i

src/plugins/e-acsl/tests/bts/bts1324.i

src/plugins/e-acsl/tests/bts/bts1326.i

src/plugins/e-acsl/tests/bts/bts1390.c

src/plugins/e-acsl/tests/bts/bts1398.c

src/plugins/e-acsl/tests/bts/bts1399.c

src/plugins/e-acsl/tests/bts/bts1478.c

src/plugins/e-acsl/tests/bts/bts1700.i

src/plugins/e-acsl/tests/bts/bts1717.i

src/plugins/e-acsl/tests/e-acsl-runtime/addrOf.i

src/plugins/e-acsl/tests/e-acsl-runtime/alias.i

src/plugins/e-acsl/tests/e-acsl-runtime/arith.i

src/plugins/e-acsl/tests/e-acsl-runtime/array.i

src/plugins/e-acsl/tests/e-acsl-runtime/at.i

src/plugins/e-acsl/tests/e-acsl-runtime/call.c

src/plugins/e-acsl/tests/e-acsl-runtime/cast.i