core does not use POSIX threads when built for the 'lx_hybrid_x86'
platform, so we need to reserve the thread-context area via a segment in
the program to prevent clashes with vdso and shared libraries.
Fixes#639.
Without this patch the compilation failed with:
/usr/bin/ld: main.o: relocation R_X86_64_32S against
`vtable for Genode::Dataspace' can not be used when making a shared object;
recompile with -fPIC
main.o: could not read symbols: Bad value
collect2: ld returned 1 exit status
make[6]: *** [init] Error 1
For this patch the use of the hardening tool chain must be indicated
using the "hardening_tool_chain" SPECS entry within the file
<build>/etc/specs.conf
Fixes#79
