build: pass --strip-all, not --strip-debug to strip

Option --strip-all will remove the static symbol section in addition to debug
symbols.  We do not need the static symbol table in libraries installed on the
target.

Change-Id: I7a52d22f5b45aa727f31bfd9af796b289528caef
Signed-off-by: Iliyan Malchev <malchev@google.com>