!44 Add URL and Source0 url

From: @eastb233
Reviewed-by: @jdkboy
Signed-off-by: @jdkboy

gcc.spec

@@ -61,7 +61,9 @@ Name: gcc
 Version: %{gcc_version}
 Release: %{DATE}.12
 License: GPLv3+ and GPLv3+ with exceptions and GPLv2+ with exceptions and LGPLv2+ and BSD
-Source0: gcc-9.3.0.tar.xz
+URL: https://gcc.gnu.org
+
+Source0: https://ftp.gnu.org/gnu/gcc/gcc-9.3.0/gcc-9.3.0.tar.xz
 %global isl_version 0.16.1
 
 BuildRoot: %{_tmppath}/%{name}-%{version}-%{release}-root-%(%{__id_u} -n)