> You need to have both glibc-mipsel.../include and
> linux-libre-headers-mipsel.../include in CROSS_CPATH.  Can you check
> whether this is the case.

Thanks, './configure' works now, I guess.  Here are the variables that I
use (don't forget about the mentioned symlinks):

LIBRARY_PATH=/root/.guix-profile/lib
CPATH=/root/.guix-profile/include
CROSS_CPATH=/nix/store/xisav2mcispg63ns8w9x5blvd14gyrd7-glibc-cross-mips64el-linux-gnu-2.17/include:/nix/store/2lzg1610m9r6kg37ja7nr5fbk6gccd9h-linux-libre-headers-cross-mips64el-linux-gnu-3.3.8/include
PATH=/nix/store/zp44ibqg7wy7rm6ipffzxx6jd1wm79fd-binutils-cross-mips64el-linux-gnu-2.23.2/bin:/root/.guix-profile/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/X11R6/bin

There is a new problem.  'make bootstrapping-files' fails:

make -r --no-print-directory -f ghc.mk bootstrapping-files

[...]

/usr/bin/find: `libraries/haskeline/dist-install/build': No such file or directory
/usr/bin/find: `libraries/haskeline/dist-install/build': No such file or directory
/usr/bin/find: `libraries/integer-gmp/dist-install/build': No such file or directory
mkdir inplace
mkdir inplace/bin
mkdir inplace/lib
"rm" -f inplace/bin/mkdirhier  
echo '#!/bin/sh'  		 >> inplace/bin/mkdirhier
cat utils/mkdirhier/mkdirhier.sh >> inplace/bin/mkdirhier
chmod +x inplace/bin/mkdirhier
Creating includes/ghcautoconf.h...
Done.
"rm" -f includes/ghcplatform.h  
Creating includes/ghcplatform.h...
Done.
"inplace/bin/mkdirhier" includes/dist-derivedconstants/build//.
  CC includes/dist-derivedconstants/build/mkDerivedConstants.o
"inplace/bin/mkdirhier" includes/dist-derivedconstants/build/tmp//.
/bin/sh: Syntax error: Unterminated quoted string
make[1]: *** [includes/dist-derivedconstants/build/tmp/mkDerivedConstants] Error 2
make: *** [bootstrapping-files] Error 2

I don't understand what causes the error.

Just for reference, I invoked the following commands:

T# cp /bin/pwd utils/ghc-pwd/ghc-pwd
T# perl boot

Then replaced '$GHC_PACKAGE_DB_FLAG' with 'package-db' in 'configure'.

T# ./configure --enable-hc-boot --target=mips64el-linux-gnu
T# cd libraries/integer-gmp
T/libraries/integer-gmp# ./configure
T/libraries/integer-gmp# cd ../..
T# cd mk
T/mk# cp build.mk.sample build.mk

After that I uncommented the following in 'build.mk':

# An unregisterised, optimised build of ghc, for porting:
BuildFlavour = unreg

T/mk# cd ..
T# make bootstrapping-files