Primary and secondary sysroot?

[Dmitry Mikushin]

Deal all,

We have a version of GCC coming as additional toolchain for several 
supported Linux distros. Moreover, package we are shipping also contains 
modified glibc and some other libraries. In this situation, applications 
built with this compiler should first logically use its own sysroot, but 
in case when a header/library from host's sysroot is needed - fallback 
to the default "/usr" sysroot. I think this could be accomplished by 
providing two sysroots - one primary, and secondary - to complement it 
for the rest of things. Looks like currently gcc only supports a single 
setting for TARGET_SYSTEM_ROOT. Do you see any other options regarding 
this issue?

Thanks,
- Dima.