3.1 fails to bootstrap on Solaris 7

[Lars Hecking]

$ cd /tmp/gcc-3.1/obj
$ ../configure --prefix=/usr/local/gcc3 --disable-nls
[...]
$ make bootstrap-lean
[...]
checking for dlfcn.h... (cached) yes
checking for backtrace... no
checking for dladdr in -ldl... yes
checking for /proc/self/exe... configure: error: Cannot check for file existence
 when cross compiling
make[1]: *** [configure-target-libjava] Error 1
make[1]: Leaving directory `/tmp/gcc-3.1/obj'
make: *** [bootstrap-lean] Error 2
$ uname -a
SunOS localhost 5.7 Generic_106541-19 sun4u sparc
$ isainfo -b
32
$

 It is possible that this problem is related to incompletely installed
 64-bit support on this machine, as I had to install a few additional
 packages to get the 64-bit archive libraries and restart the compile.
 Other than that, I have no idea why configure thinks _at_this_stage_
 that it's cross-compiling.