[clang-repl] Fix Value for platforms where unqualified char is unsigned (#86118)

Signedness of unqualified `char` is unspecified and varies between
platforms. This patch adds `Char_U` in `REPL_BUILTIN_TYPES` to account
for platforms that default to `unsigned char`.

Author: weliveindetail

clang/include/clang/Interpreter/Value.h

@@ -76,6 +76,7 @@ class QualType;
   X(bool, Bool)                                                                \
   X(char, Char_S)                                                              \
   X(signed char, SChar)                                                        \
+  X(unsigned char, Char_U)                                                     \
   X(unsigned char, UChar)                                                      \
   X(short, Short)                                                              \
   X(unsigned short, UShort)                                                    \

clang/unittests/Interpreter/InterpreterTest.cpp

@@ -340,6 +340,12 @@ TEST(InterpreterTest, Value) {
   EXPECT_EQ(V1.getKind(), Value::K_Int);
   EXPECT_FALSE(V1.isManuallyAlloc());
 
+  Value V1b;
+  llvm::cantFail(Interp->ParseAndExecute("char c = 42;"));
+  llvm::cantFail(Interp->ParseAndExecute("c", &V1b));
+  EXPECT_TRUE(V1b.getKind() == Value::K_Char_S ||
+              V1b.getKind() == Value::K_Char_U);
+
   Value V2;
   llvm::cantFail(Interp->ParseAndExecute("double y = 3.14;"));
   llvm::cantFail(Interp->ParseAndExecute("y", &V2));