Include and lib search paths

[Edward Diener <eldlistmailingz@xxxxxxxxxxxxxx>]

I use both Windows and Linux. On Windows when using mingw or mingw-64 I 
noticed that the search paths for include directories and lib 
directories were hardcoded to c:\mingw. This fact makes it much harder 
to run multiple versions of gcc on Windows. When I asked why absolute 
hardcoded paths were used instead of relative paths to the gcc 
installation I was told this was because gcc itself did it this way.

So now I ask here. Why does gcc use hardcoded absolute paths to include 
and lib directories when relative paths within a gcc installation would 
make gcc much more portable and would make it much easier for multiple 
versions of gcc to co-exist ?