go-native: fix import error when len(TMPDIR) == 410

go-native: fix import error when len(TMPDIR) == 410

It is used for saving file path, 500 is a little small when building in deep
path, for example, it would be failed when oe-coe's len(TMPDIR) == 410, use
1000 can fix the problem.

Fixed:
$ bitbake go-native
[snip]
gcc -isystem/workspace2/lyang1/aaaaaaaa/[snip]
exec gcc: No such file or directory
[snip]

Only go-native needs this patch since only it uses go1.4 which has src/cmd/gc/go.h.

[YOCTO #11351]

Signed-off-by: Robert Yang <liezhi.yang@windriver.com>