Do not strip static libraries shipped with the SDK in order to preserve the
archive index. If we strip the index of the shipped libraries, host programs
will fail to link these libraries with errors like:

    libssl.a: error adding symbols: Archive has no index; run ranlib to add one

The error was found while investigating a Python host build failure within
the SDK environment.

Signed-off-by: Jo-Philipp Wich <jo@mein.io>