test: workaround possible GCC bug with non-const variable templates

Author: JohelEGP

regression-tests/pure2-template-specialization.cpp2

@@ -7,8 +7,8 @@ t: @struct <T: type> specialize<T> type requires std::is_void_v<T> = {
 t: @struct specialize<i64> type = {
   c: i32 = 3;
 }
-v: <T> i32 = 1;
-v: <> specialize<void> i32 = 2;
+v: <T> const i32 = 1;
+v: <> specialize<void> const i32 = 2;
 main: ()   = {
   [[assert Testing: t<i32>().a == 1]]
   [[assert Testing: t<void>().b == 2]]

regression-tests/test-results/gcc-13/pure2-template-specialization.cpp.execution

@@ -22,7 +22,7 @@ template<typename T> requires( std::is_void_v<T> )
 template<> class t<cpp2::i64> {
   public: cpp2::i32 c {3}; 
 };
-template<typename T> extern cpp2::i32 v;
+template<typename T> extern cpp2::i32 const v;
 
 auto main() -> int;
 
@@ -31,8 +31,8 @@ auto main() -> int;
 
 
 #line 10 "pure2-template-specialization.cpp2"
-template<typename T> cpp2::i32 v {1}; 
-template<> cpp2::i32 v<void> {2}; 
+template<typename T> cpp2::i32 const v {1}; 
+template<> cpp2::i32 const v<void> {2}; 
 auto main() -> int{
   cpp2::Testing.expects(t<cpp2::i32>().a==1, "");
   cpp2::Testing.expects(t<void>().b==2, "");