configure script extention with option --srcdir

[pkleymonov-qnx]

It is very convenient and consistent to provide additional option like --srcdir.

It helps to cross build perl from different sources and keep perl sources clean.

For instance, sometimes it needs to cross build for several platforms like arm7, aarch64, x86, x86_64 etc.
And it will better correspond to autotool concept, which provides this option inside generated ./configure script.

Nested ./configure script execution

../../configure --srcdir=<path_to_the_perl_source_tree>

See: https://buildsystem-manual.sourceforge.net/configure-Invocation.html#configure-Invocation