If polymake is to be installed, install gcc if systen gcc < 5.1

Author: Matthias Koeppe

build/pkgs/polymake/spkg-configure.m4

@@ -0,0 +1,10 @@
+SAGE_SPKG_CONFIGURE([polymake], [
+    sage_spkg_install_polymake=yes
+    AC_REQUIRE([SAGE_SPKG_CONFIGURE_GCC])
+    if test $IS_REALLY_GCC = yes ; then
+       AC_MSG_NOTICE([checking if gcc version is at least 5.1 for polymake])
+       AS_CASE(["$GXX_VERSION.0"],
+           [[[0-4]].*|5.0.*], [
+               SAGE_MUST_INSTALL_GCC([you have $CXX version $GXX_VERSION, which is too old to build polymake])
+                ])
+    fi])