configure --with-sysroot

[<gp at qnx dot com>]

Hi.

I am working on support for QNX6.  Our cross development system files are laid
out so we don't have a single TARGET_SYSTEM_ROOT, but rather we have a
TARGET_HEADER_ROOT and a different TARGET_LIB_ROOT.  

For example, on i386-qnx-nto targetting armle-qnx-nto, we have:

 ${TARGET_SYSTEM_ROOT}/lib           # Native lib dir
 ${TARGET_SYSTEM_ROOT}/usr/include   # Common headers for all targets
 ${TARGET_SYSTEM_ROOT}/armle/lib     # armle lib
 ${TARGET_SYSTEM_ROOT}/armle/usr/lib # armle usr/lib

I had set things up to use the existing --with-sysroot, and then in my t-nto
file I set up a QNX_SYSTEM_ROOT define which I use in my LIB_SPEC to build a
set of '-L' lines:

   "-L " QNX_SYSTEM_ROOT "/arm%{EB:be}%{!EB:le}/lib \
    -L " QNX_SYSTEM_ROOT "/arm%{EB:be}%{!EB:le}/usr/lib "

This works except we have incompatible native libs in
${TARGET_SYSTEM_ROOT}/lib and ${TARGET_SYSTEM_ROOT}/usr/lib.  Then I get all
kinds of warnings about "skipping incompatible file libc.so" from the linker.

1) Is there a way to prepend (as opposed to append) a search path to gcc's
binary/lib search path from within the specs file?  Like "-B" does on the
command line?  That way I can get the armle/lib dirs searched first.

2) If not, would anyone strongly oppose my adding a --with-hdrsysroot and
--with-libsysroot (overridden by --with-sysroot) to gcc/configure.in et al?

Thanks.
GP