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>

 # Compute AVR32-specific values

 CT_DoArchTupleValues() {

     # gcc ./configure flags

     CT_ARCH_WITH_ARCH=

     CT_ARCH_WITH_ABI=

     CT_ARCH_WITH_CPU=

     CT_ARCH_WITH_TUNE=

     CT_ARCH_WITH_FPU=

     CT_ARCH_WITH_FLOAT=

     CT_TARGET_SYS=none

 }