libc/glibc: fix installing syscall.h when installing start-files.

Reported-by: Rafael C <groups.r2@gmail.com>
Reported-by: Jérôme BARDON <bardon.pro@gmail.com>
Reported-by: Daniel Price <daniel.price@gmail.com>
[yann.morin.1998@free.fr: use a conditional approach, also suggested by Daniel]
Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>

CT_EXPERIMENTAL=y

CT_LOCAL_TARBALLS_DIR="${HOME}/src"

CT_SAVE_TARBALLS=y

CT_LOG_EXTRA=y

CT_ARCH_CPU="cpu32"

CT_ARCH_m68k=y

CT_ARCH_BINFMT_FLAT=y

CT_BINUTILS_V_2_20_1a=y

CT_CC_V_4_3_4=y

CT_LIBC_none=y

CT_GMP_V_4_3_2=y

CT_MPFR_V_2_4_2=y