complibs/ppl: only add -fpermissive flag to CXXFLAGS

-fpermissive is not a valid option to gcc.

Adding it to the CFLAGS make the ppl checks fail with the following
error:

[ALL ] Making check in tests
[ALL ] cc1: warnings being treated as errors
[ERROR] cc1: error: command line option "-fpermissive" is valid for C++/ObjC++ but not for C
[ALL ] cc1: warnings being treated as errors
[ERROR] cc1: error: command line option "-fpermissive" is valid for C++/ObjC++ but not for C
[ERROR] make[7]: *** [formatted_output.o] Error 1

Signed-off-by: "Samuel Martin" <smartin@aldebaran-robotics.com>
Message-Id: <bba2482a06a11415207e.1365876457@smartin-de-2.aldebaran.lan>
Patchwork-Id: 236383

 # dmalloc debug facility

 ## depends on ! BACKEND

 ##

 ## help dmalloc helps tracking memory allocation mis-usage

 ## help such as double-free, use-after-free...

 choice

     bool

     prompt "dmalloc version"

 # Don't remove next line

 # CT_INSERT_VERSION_BELOW

 config DMALLOC_V_5_5_2

     bool

     prompt "5.5.2"

 endchoice

 config DMALLOC_VERSION

     string

 # Don't remove next line

 # CT_INSERT_VERSION_STRING_BELOW

     default "5.5.2" if DMALLOC_V_5_5_2