[clang] Clang/MIPS: Use -mnan value for -mabs if not specified (PR #71157)

[Fangrui Song via cfe-commits]

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@@ -214,6 +214,14 @@
 // RUN:     -mnan=legacy -mnan=2008 2>&1 \
 // RUN:   | FileCheck --check-prefix=CHECK-NAN2008 %s
 // CHECK-NAN2008: "-target-feature" "+nan2008"
+// CHECK-NAN2008: "-target-feature" "+abs2008"
+//
+// -mnan=2008 -mabs=legacy
+// RUN: %clang -target mips-linux-gnu -march=mips32r3 -### -c %s \
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MaskRay wrote:

`--target=`

https://github.com/llvm/llvm-project/pull/71157