complibs/ppl: remove unnecessary (and confusing) --enable-cxx configure switch.

PPL does not use the "--enable-cxx" configure switch at all; it's
possibly a cut-and-paste leftover from 'gmp.sh'. (PPL is written in C++
natively, so it doesn't make much sense to have to enable C++; GMP, on
the other hand, is written in C with an optional C++ wrapper.)

Signed-Off-By: Anthony Foiani <anthony.foiani@gmail.com>

 syntax: glob

 # Generated files

 Makefile

 ct-ng

 docs/ct-ng.1

 docs/ct-ng.1.gz

 paths.mk

 scripts/crosstool-NG.sh

 scripts/saveSample.sh

 scripts/showTuple.sh

 kconfig/conf

 kconfig/?conf

 kconfig/**.o

 kconfig/**.dep

 config.gen/

 .config

 # Temporaries

 .*.swp

 build.log

 .config.old

 # This is the place where toolchains are built

 .build/

 # .. and the legacy location

 targets/