[llvm] [UTC] Escape multiple {{ or }} in input for check lines. (PR #71790)

[Nikita Popov via llvm-commits]

================
@@ -81,7 +81,7 @@ define void @test_brace_escapes(ptr noundef %arr) {
 ; CHECK-NEXT:      Grouped accesses:
 ; CHECK-NEXT:        Group [[GRP4]]:
 ; CHECK-NEXT:          (Low: {(64 + %arr),+,64}<%loop.1> High: {(8064 + %arr),+,64}<%loop.1>)
-; CHECK-NEXT:            Member: {{(64 + %arr),+,64}<%loop.1>,+,8}<%loop.2>
+; CHECK-NEXT:            Member: {{\{{}}(64 + %arr),+,64}<%loop.1>,+,8}<%loop.2>
----------------
nikic wrote:

Is this the correct result? Shouldn't this be `{{\{\{}}`?

https://github.com/llvm/llvm-project/pull/71790