[Yhc] Building yhc failed

[Echaozh Zhang]

I'm trying to build yhc on my debian machine. When I'm executing scons
build, it reports the following error:

$ scons build
scons: Reading SConscript files ...
Building version 0.7.0-20061129043224-custom.
Checking for architecture... (cached) x86
Checking for operating system... (cached) linux2
Checking for C header file gmp.h... (cached) yes
Checking for mpz_t integ; mpz_init (integ) in C library gmp... (cached) yes
Checking for libgmp version... (cached)
Bootstrapping...
build/SConscript.depends -> depends/SConscript
build/SConscript.cpphs -> depends/cpphs/SConscript
build/SConscript.filepath -> depends/filepath/SConscript
build/SConscript.ctypes -> depends/ctypes/SConscript
build/SConscript.libffi -> depends/ctypes/libffi/SConscript
build/ffih/fficonfig.h -> depends/ctypes/libffi/fficonfig.h
build/ffih/ffi.h -> depends/ctypes/libffi/include/ffi.h
build/ffih/cfield.c -> depends/ctypes/libffi/src/cfield.c
bootstrap/packages/yhc-base/1.0/Prelude.hi ->
src/packages/yhc-base-1.0/Prelude.hi
bootstrap/packages/yhc-base/1.0/PreludeBuiltin.hi ->
src/packages/yhc-base-1.0/PreludeBuiltin.hi
bootstrap/packages/yhc-base/1.0/YHC/Internal.hi ->
src/packages/yhc-base-1.0/YHC/Internal.hi
bootstrap/packages/yhc-base/1.0/Data/Ratio.hi ->
src/packages/yhc-base-1.0/Data/Ratio.hi
Done.
scons: done reading SConscript files.
scons: Building targets ...
Getting dependencies for src/compiler98/Bind.hs.
Getting dependencies for src/compiler98/Util/Text.hs.
ghc -i./src/compiler98 -i./src/libraries/general
-i./src/libraries/core -idepends/cpphs -idepends/filepath
-i./src/interactive -package mtl -fwarn-missing-signatures -c
src/compiler98/Util/Text.hs -o src/compiler98/Util/Text.o
ghc-6.6: unknown package: mtl
scons: *** [src/compiler98/Util/Text.o] Error 1
scons: building terminated because of errors.

What's the problem? Can anyone help me with it?