Add support for AIX noipath option to ld

[Ådne Hovda <ahovda at openit dot com>]

Hi

I've set up a Binutils/GCC cross compiler for Linux -> AIX and have some 
issues with the LIBPATH for individual members when putting full path to 
system libraries from the sys-root on the linker line.

Compiling like this:

powerpc-ibm-aix5.1.0.0-gcc xhello.c /mytoolchain/usr/lib/libX11.a 
-Wl,-blibpath:"/usr/lib:/lib"

Produces an import section like this:
                        ***Import File Strings***
INDEX  PATH                          BASE                MEMBER
0      /usr/lib:/lib
1                                    libc.a              shr.o
2      /mytoolchain/usr/lib          libX11.a            shr4.o


The native AIX linker has the noipath option, which results in:
                        ***Import File Strings***
INDEX  PATH                          BASE                MEMBER
0      /usr/lib:/lib
1                                    libc.a              shr.o
2                                    libX11.a            shr4.o

Which is what I'm after. Please note that the regular libpath/nolibpath 
options have no effect on these search paths.

From the ld man page on AIX:
> noipath For shared objects listed on the command-line, rather than specified
> with the -l flag, use a null path component when listing the shared object in
> the loader section of the output file. A null path component is always used for
> shared objects specified with the -l flag.

I guess this is considered an edge-case, and I don't expect a lot of 
support, but any pointers as to where in the code to start looking will 
be greatly appreciated.

Best regards,
Ådne Hovda