[clang] [llvm] Enable fexec-charset option (PR #138895)

[Hubert Tong via cfe-commits]

================
@@ -217,8 +217,14 @@
 // RUN: not %clang -### -S -finput-charset=iso-8859-1 -o /dev/null %s 2>&1 | FileCheck -check-prefix=CHECK-INVALID-CHARSET %s
 // CHECK-INVALID-CHARSET: error: invalid value 'iso-8859-1' in '-finput-charset=iso-8859-1'
 
-// RUN: not %clang -### -S -fexec-charset=iso-8859-1 -o /dev/null %s 2>&1 | FileCheck -check-prefix=CHECK-INVALID-INPUT-CHARSET %s
-// CHECK-INVALID-INPUT-CHARSET: error: invalid value 'iso-8859-1' in '-fexec-charset=iso-8859-1'
+// RUN: %clang -### -S -fexec-charset=invalid-charset -o /dev/null %s 2>&1 | FileCheck -check-prefix=CHECK-INVALID-INPUT-CHARSET %s
+// CHECK-INVALID-INPUT-CHARSET: error: invalid value 'invalid-charset' in '-fexec-charset=invalid-charset'
+
+// Test that we support the following exec charsets.
+// RUN: %clang -### -S -fexec-charset=UTF-8 -o /dev/null %s 2>&1 | FileCheck --check-prefix=INVALID %s
+// RUN: %clang -### -S -fexec-charset=ISO8859-1 -o /dev/null %s 2>&1 | FileCheck --check-prefix=INVALID %s
+// RUN: %clang -### -S -fexec-charset=IBM-1047 -o /dev/null %s 2>&1 | FileCheck --check-prefix=INVALID %s
+// INVALID-NOT: error: invalid value
----------------
hubert-reinterpretcast wrote:

```suggestion
// RUN: not %clang -### -S -fexec-charset=invalid-charset -o /dev/null %s 2>&1 | FileCheck -check-prefix=CHECK-INVALID-EXEC-CHARSET %s
// CHECK-INVALID-EXEC-CHARSET: error: invalid value 'invalid-charset' in '-fexec-charset=invalid-charset'

// Test that we support the following exec charsets.
// RUN: %clang -### -S -fexec-charset=UTF-8 -o /dev/null %s 2>&1 | FileCheck --check-prefix=CHECK-VALID-EXEC-CHARSET %s
// RUN: %clang -### -S -fexec-charset=IBM-1047 -o /dev/null %s 2>&1 | FileCheck --check-prefix=CHECK-VALID-EXEC-CHARSET %s
// CHECK-VALID-EXEC-CHARSET-NOT: error: invalid value
```

https://github.com/llvm/llvm-project/pull/138895