scripts/functions: use portable 'gzip -dc'

'zcat' on MacOS-X is broken (it is not gzip's zcat, but compres' zcat).

Use 'gzip -dc' for portability, as suggested by Anthony.

Reported-by: Fernando Ortiz <fortiz2k@gmail.com>
Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Cc: Anthony Foiani <anthony.foiani@gmail.com>

CT_LOCAL_TARBALLS_DIR="${HOME}/src"

CT_SAVE_TARBALLS=y

CT_LOG_EXTRA=y

CT_ARCH_BE=y

CT_ARCH_FLOAT_SW=y

CT_ARCH_arm=y

CT_BINUTILS_V_2_19_1a=y

CT_CC_V_4_3_2=y

CT_LIBC_none=y

CT_DEBUG_gdb=y

CT_GDB_V_6_8a=y

CT_GMP_V_4_3_2=y

CT_MPFR_V_2_4_2=y