feat(backend/riscv32): 实现基础的编译器功能

- 完成 RV32IMA 指令集的代码生成
- 添加整数运算、分支、调用等基本指令支持
- 实现从 IR 到机器码的转换
- 添加简单的测试用例和测试框架

ccompiler/frontend/lexer/lexer.c

@@ -163,13 +163,14 @@ static void parse_char_literal(lexer_t* lexer, tok_t* token) {
     if (*peek == '\\') {
         peek++;
         val = got_slash(peek);
+        peek++;
     } else {
-        val = *peek;
+        val = *peek++;
     }
 
-    if (*peek != '\'') error("Unclosed character literal");
+    if (*peek++ != '\'') error("Unclosed character literal");
     token->val.ch = val;
-    lexer->cur_ptr = peek + 1;
+    lexer->cur_ptr = peek;
     token->val.have = 1;
     token->type = TOKEN_CHAR_LITERAL;
 }