Evaluate portability on MacOSX

[svalat]

I got some reports on what is currently not working to build under MacOSX:

• xargs command not available, should use gxargs in ./configure script.
• MAP_POPULATE note available for mmap in SimpleAllocator & OSUnix.cpp.
• Compilation problem with libelf from the system (link.h not found ad issues when using /Library/Developer/CommandLineTools/SDKs/MacOSX14.2.sdk/usr/include/link.h instead. Can be an issue to handle the address to source line part.
• The lib destructor annotation (__attribute__ ((destructor())) looks not supported.
• There was issues repported when using clang so the try was done with gcc.
• Handle the replacement of LD_PRELOAD by DYLD_INSERT_LIBRARIES
• Handle right replacement for spinlocks