dash : convert to autotools infrastructure & bump to 0.5.5.1

Changes by Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

 * No need to strip
 * Target installation is the default
 * No installation to staging is the default
 * Remove DASH_BINARY/DASH_SOURCE variables
 * Fix minor mistakes
 * Simplify: no need to pass CC/CC_FOR_BUILD

Signed-off-by: cmchao <cmchao@gmail.com>

merge dash