if [[ ! -f $BT_TESTS_BUILDDIR/Makefile ]]; then
{
echo "ERROR: Invalid \`BT_TESTS_BUILDDIR\` variable (\`\$BT_TESTS_BUILDDIR/Makefile\`"
if [[ ! -f $BT_TESTS_BUILDDIR/Makefile ]]; then
{
echo "ERROR: Invalid \`BT_TESTS_BUILDDIR\` variable (\`\$BT_TESTS_BUILDDIR/Makefile\`"