remove hardcoded arm flags for android, and instead of patching the
sources, rather specify the desired values on commandline to override
nss' makefile defaults where possible.
Also since the build stage runs nspr configure by itself in a dedicated
outdir, the separate configure step was removed (for all systems).

Change-Id: I586c605615cc2d45b757497395a98c53dd1beb1d
Reviewed-on: https://gerrit.libreoffice.org/42070Reviewed-by: Christian Lohmaier <lohmaier+LibreOffice@googlemail.com>
Tested-by: Christian Lohmaier <lohmaier+LibreOffice@googlemail.com>