debug/ltrace: fix building for mips

ltrace 0.5.3 currently fails to build for target mips because MY_TARGET
(introduced by patches/ltrace/0.5.3/150-allow-configurable-arch.patch)
is set to 'mips' via CT_ARCH, while the mips specific stuff in ltrace
(0.5.3) is stored under sysdeps/linux-gnu/mipsel:

result: *** No rule to make target `mips/arch.h', needed by `sysdep.h'.
Stop.

The following patch fixes this issue

Signed-off-by: "Horst Kronstorfer" <horst.kronstorfer@aon.at>
[yann.morin.1998@anciens.enib.fr: reformat commit log]
Signed-off-by: "Yann E. MORIN" <yann.morin.1998@anciens.enib.fr>

     1.1 --- a/scripts/build/debug/400-ltrace.sh	Sat Jan 08 17:58:23 2011 +0100
     1.2 +++ b/scripts/build/debug/400-ltrace.sh	Sat Jan 08 18:07:02 2011 +0100
     1.3 @@ -33,6 +33,7 @@
     1.4              x86:32)     ltrace_host="i386";;
     1.5              x86:64)     ltrace_host="x86_64";;
     1.6              powerpc:*)  ltrace_host="ppc";;
     1.7 +            mips:*)     ltrace_host="mipsel";;
     1.8              *)          ltrace_host="${CT_ARCH}";;
     1.9          esac
    1.10          CC="${CT_TARGET}-${CT_CC}"      \