[clang] [clang] Enable descriptions for --print-supported-extensions (PR #66715)

[David Spickett via cfe-commits]

================
@@ -4,14 +4,17 @@
 // RUN: %if aarch64-registered-target %{ %clang --target=aarch64-linux-gnu \
 // RUN:   --print-supported-extensions 2>&1 | FileCheck %s --check-prefix AARCH64 %}
 // AARCH64: All available -march extensions for AArch64
+// AARCH64:     Name                Description
 
 // RUN: %if riscv-registered-target %{ %clang --target=riscv64-linux-gnu \
 // RUN:   --print-supported-extensions 2>&1 | FileCheck %s --check-prefix RISCV %}
 // RISCV: All available -march extensions for RISC-V
+// RISCV:     Name                Version   Description
 
 // RUN: %if arm-registered-target %{ %clang --target=arm-linux-gnu \
 // RUN:   --print-supported-extensions 2>&1 | FileCheck %s --check-prefix ARM %}
 // ARM: All available -march extensions for ARM
+// ARM:     Name                Description
----------------
DavidSpickett wrote:

E.g.
```
ARM:     crc                 Enable support for CRC instructions
```
Then if we ever added `arc` it wouldn't matter if it came first, we're still checking the important things.

https://github.com/llvm/llvm-project/pull/66715