Currently, if:
* GCC doesn't supports -no-pie: Build error
* GCC supports -no-pie
* GCC is not configured with --enable-default-pie: No-op
* GCC is configured with --enable-default-pie:
Slightly worse performance because we still generate -fpie code
(-pie affects linker, -fpie affects compiler)
So instead of probing for existence of -fno-pie -no-pie, remove it altogether.
Fixes#540: Build breakage on Debian 8 with gcc 4.9.
