[clang] [Driver] Add -Wa, options --crel and --allow-experimental-crel (PR #97378)

[Fangrui Song via cfe-commits]

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+// RUN: not %clang -### -c --target=x86_64 -Wa,--crel %s 2>&1 | FileCheck %s --check-prefix=NOEXP
+
+// NOEXP: error: -Wa,--allow-experimental-crel must be specified to use -Wa,--crel. CREL is experimental and takes a non-standard section type code
+
+// RUN: %clang -### -c --target=x86_64 -Wa,--crel,--allow-experimental-crel %s -Werror 2>&1 | FileCheck %s
+// RUN: %clang -### -c --target=x86_64 -Wa,--crel,--no-crel,--allow-experimental-crel %s -Werror 2>&1 | FileCheck %s --check-prefix=NO
+// RUN: %clang -### -c --target=x86_64 -Wa,--allow-experimental-crel %s -Werror 2>&1 | FileCheck %s --check-prefix=NO
+// RUN: not %clang -### -c --target=arm64-apple-darwin -Wa,--crel,--allow-experimental-crel %s 2>&1 | FileCheck %s --check-prefix=ERR
+// RUN: not %clang -### -c --target=mips64 -Wa,--crel,--allow-experimental-crel %s 2>&1 | FileCheck %s --check-prefix=ERR
+
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MaskRay wrote:

Good idea. Added

https://github.com/llvm/llvm-project/pull/97378