zx2c4@thinkpad ~ $ audacity Fatal Error: Mismatch between the program and library build versions detected. The library used 2.8 (no debug,Unicode,compiler with C++ ABI 1002,wx containers,compatible with 2.6), and your program used 2.8 (no debug,Unicode,compiler with C++ ABI 1009,wx containers,compatible with 2.6). Aborted Using gcc 5.3. Recompiling either wxGTK or Audacity does not fix the problem.
I think you should rebuild everything C++: https://wiki.gentoo.org/wiki/Upgrading_from_gcc-4.x_to_gcc-5.x it works fine here