Would it make sense to have sysroot come from an environment variable?

[Bryan Ischo]

I'm still trying to get my head around all of the search paths that the 
GNU toolchain uses and when it uses them and how it gets them.  I'm 
wondering if it makes any sense at all for the toolchain to accept 
sysroot via an environment variable; for the purposes of this discussion 
I would propose that this variable be SYSROOT.

I suggest this only because I'm trying to create a fairly self-contained 
build of the compiler toolchain that is as 'relocatable' as possible, 
and one problem is that I can put libraries and headers (for gcc, glibc, 
and the kernel) into a sysroot directory of my choosing that I can move 
around as I need to, but then making the toolchain use that sysroot 
requires passing --sysroot flags to the appropriate tool at the 
appropriate time; and it seems like since the sysroot would be a fixed 
value that would be used identically for all tools in the toolchain, 
getting this value from an environment variable would be much more 
convenient and seamless.

Would it make any sense to do this?  If so, would it be as simple as 
patching the tools to look at a SYSROOT environment variable to get 
their sysroot if none has been specified on the command line?

Thank you, and best wishes,
Bryan