Major Linux distributions do not provide LLVM libc++, because:
- Unlike Apple and FreeBSD, the GPL+3 is not an issue, so no need to
implement another stack here.
- Linux components have been developed around GNU libstd++ for ages. Some of them
do not build on anything else.
- While libc++ is strong in new features, it has some problems with legacy code.
If eventually libc++ became part of distributions, it will be as an optional component. linking against it will probably require extra options.
Like Jonathan said, you should use whatever tool is included by default. Clang is safe in Linux to use since is configured as a GCC replacement, so in that aspect you don't have to worry about 2 compilers. Also since you are targeting two platforms, you should take a look to cmake.