[libc] Fix gmtime test on systems with sizeof(time_t) == 4 (#65388)

This test creates a time_t variable and assigns 0xfffffffffe1d7b01 which
overflows the maximum time_t value for 64-bit time_t, then checks if the
syscall fails and errno was set.

In systems with sizeof(time_t) == 4, the value is narrowed down to
0xfe1d7b01 and doesn't overflow, causing the test to fail.

This patch then disables the test on systems with 32 bits long time_t.