Here is the output:
  CC    prescr.lo
  CC    seive.lo
  LD    libgretl-1.0.la
make[1]: Leaving directory `/home/helio/gretl/lib'
make -C cli
make[1]: Entering directory `/home/helio/gretl/cli'
  CC    gretlcli.o
  CC    complete.o
  LD    gretlcli
../lib/.libs/libgretl-1.0.so: undefined reference to `g_get_monotonic_time'
collect2: ld returned 1 exit status
make[1]: *** [gretlcli] Error 1
make[1]: Leaving directory `/home/helio/gretl/cli'
make: *** [cli] Error 2

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Searching in Internet for g_get_monotonic_time, I see that it belongs in GTK+, but even in GTK 2, is there.

Well, there is now a CentOS 7 released, maybe if I upgrade, this gets solved.

Hélio