If you specify something like --cc="ccache gcc" on your configure line
the summary output misses the rest of the cmd_array. Do some string
joining to make it complete.

Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Tested-by: Thomas Huth <thuth@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20210527160319.19834-3-alex.bennee@linaro.org>