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>
(transplanted from 2115901c7f07181d92ddbd7dd7ebeaa72e4fb176)

 # Compute IA-64-specific values

 CT_DoArchTupleValues() {

     # The architecture part of the tuple, override only for 64-bit

     if [ "${CT_ARCH_64}" = "y" ]; then

         CT_TARGET_ARCH="mips64${target_endian_el}"

     else

         # The architecture part of the tuple:

         CT_TARGET_ARCH="${CT_ARCH}${target_endian_el}"

     fi

     # Override CFLAGS for endianness:

     case "${CT_ARCH_BE},${CT_ARCH_LE}" in

         y,) CT_ARCH_ENDIAN_CFLAG="-EB";;

         ,y) CT_ARCH_ENDIAN_CFLAG="-EL";;

     esac

     # Override ABI flags

     CT_ARCH_ABI_CFLAG="-mabi=${CT_ARCH_mips_ABI}"

     CT_ARCH_WITH_ABI="--with-abi=${CT_ARCH_mips_ABI}"

 }