Linux/PA-RISC: Link with --unique=.text.* to help binutils

There is a binutils bug that leads to errors like this:

/usr/lib/gcc/hppa2.0-unknown-linux-gnu/4.6.3/../../../../hppa2.0-unknown-linux-gnu/bin/ld: libCMakeLib.a(cmTarget.cxx.o)(.text+0x12084): cannot reach 00001d28__ZNSspLEPKc@@GLIBCXX_3.4+0, recompile with -ffunction-sections
/usr/lib/gcc/hppa2.0-unknown-linux-gnu/4.6.3/../../../../hppa2.0-unknown-linux-gnu/bin/ld: libCMakeLib.a(cmTarget.cxx.o)(.text+0x12084): cannot handle R_PARISC_PCREL17F for std::basic_string<char, std::char_traits<char>, std::allocator<char> >::operator+=(char const*)@@GLIBCXX_3.4
/usr/lib/gcc/hppa2.0-unknown-linux-gnu/4.6.3/../../../../hppa2.0-unknown-linux-gnu/bin/ld: final link failed: Bad value

Until someone finds out what needs to be fixed in binutils this allows anyone
to compile a working CMake even in debug mode.