make tagName that is null-terminated even with the stage1 compiler

Author: vole-dev

lib/std/target.zig

@@ -699,10 +699,27 @@ pub const Target = struct {
                 .spirv64 => .spirv64,
             };
         }
+
+        // re-implementing @tagName because @tagName is not null-terminated in the stage1 compiler
+        fn tagName(value: anytype) [:0]const u8 {
+            const T = @TypeOf(value);
+            const info = @typeInfo(T);
+
+            switch (info) {
+                .Enum => |enum_info| {
+                    comptime var names: [enum_info.fields.len][:0]const u8 = undefined;
+                    inline for (enum_info.fields) |field, i| {
+                        names[i] = field.name ++ [0:0]u8{};
+                    }
+                    return names[@enumToInt(value)];
+                },
+                else => @compileError("tagName does no support type " ++ @typeName(T) ++ "."),
+            }
+        }
         pub fn string(self: TargetAbi) ?[:0]const u8 {
             switch (self) {
-                .riscv32 => |abi| return @tagName(abi),
-                .riscv64 => |abi| return @tagName(abi),
+                .riscv32 => |abi| return tagName(abi),
+                .riscv64 => |abi| return tagName(abi),
                 else => return null,
             }
         }