Trac #34857: bump giac's GIAC_MIN_VERSION to 1.9

some distro's e.g. Fedora 34, carry giac 1.7, which is too old

URL: https://trac.sagemath.org/34857
Reported by: dimpase
Ticket author(s): Matthias Koeppe
Reviewer(s): Dima Pasechnik

build/pkgs/giac/spkg-configure.m4

@@ -1,7 +1,7 @@
 SAGE_SPKG_CONFIGURE([giac], [
     SAGE_SPKG_DEPCHECK([pari], [
        dnl giac does not seem to reveal its patchlevel
-       m4_pushdef([GIAC_MIN_VERSION], [1.5.0])
+       m4_pushdef([GIAC_MIN_VERSION], [1.9.0])
        m4_pushdef([GIAC_MAX_VERSION], [1.9.999])
        AC_CACHE_CHECK([for giac >= ]GIAC_MIN_VERSION[, <= ]GIAC_MAX_VERSION, [ac_cv_path_GIAC], [
          AC_PATH_PROGS_FEATURE_CHECK([GIAC], [giac], [