gcc alpha target with mips source to compile

[Artifex Maximus]

Hello!

I got the following strange (at least to me) effect. I would like to
compile gcc 4.5.2 targeting alpha on Debian 6 x86_64. My configuration
line:

configure \
 -v \
 --build=x86_64-linux-gnu \
 --host=x86_64-linux-gnu \
 --target=alpha-dec-osf4.0f \
 --enable-obsolete \
 --enable-languages=c,c++ \
 --prefix=/usr \
 --disable-multiarch \
 --disable-multilib \
 --disable-shared \
 --disable-nls \
 --enable-checking=release

Compile ends at the following line:

x86_64-linux-gnu-gcc -c  -g -O2 -DIN_GCC -DCROSS_DIRECTORY_STRUCTURE
-W -Wall -Wwrite-strings -Wcast-qual -Wstrict-prototypes
-Wmissing-prototypes -Wmissing-format-attribute -pedantic
-Wno-long-long -Wno-variadic-macros -Wno-overlength-strings
-Wold-style-definition -Wc++-compat  -Wno-error -DHAVE_CONFIG_H -I.
-I. -I/home/system/src/gcc/bld/../src/gcc/gcc
-I/home/system/src/gcc/bld/../src/gcc/gcc/.
-I/home/system/src/gcc/bld/../src/gcc/gcc/../include
-I/home/system/src/gcc/bld/../src/gcc/gcc/../libcpp/include
-I/home/system/src/gcc/bld/gcc-build/./gmp
-I/home/system/src/gcc/src/gcc/gmp
-I/home/system/src/gcc/bld/gcc-build/./mpfr
-I/home/system/src/gcc/src/gcc/mpfr
-I/home/system/src/gcc/src/gcc/mpc/src
-I/home/system/src/gcc/bld/../src/gcc/gcc/../libdecnumber
-I/home/system/src/gcc/bld/../src/gcc/gcc/../libdecnumber/dpd
-I../libdecnumber
/home/system/src/gcc/bld/../src/gcc/gcc/mips-tfile.c -o mips-tfile.o
/home/system/src/gcc/bld/../src/gcc/gcc/mips-tfile.c:673:24: error:
mips/a.out.h: No such file or directory
/home/system/src/gcc/bld/../src/gcc/gcc/mips-tfile.c:692: error:
‘scNil’ undeclared here (not in a function)
...
/home/system/src/gcc/bld/../src/gcc/gcc/mips-tfile.c:5405: error:
‘page_t’ has no member named ‘thead’
make[2]: *** [mips-tfile.o] Error 1
make[2]: Leaving directory `/home/system/src/gcc/bld/gcc-build/gcc'
make[1]: *** [all-gcc] Error 2
make[1]: Leaving directory `/home/system/src/gcc/bld/gcc-build'
make: *** [all] Error 2

Why alpha target try to compile any mips related file?

Is gcc 4.6.0 does not support osf4.0f target? Because I cannot compile
with the same configure line.

Bye,
a