[llvm][test] Write temporary files to %t instead of CWD

Author: gribozavr

llvm/test/Other/cfg-multiline-header.ll

@@ -1,5 +1,7 @@
-; RUN: opt < %s -passes=dot-cfg -cfg-dot-filename-prefix=cfg 2>/dev/null > /dev/null
-; RUN: FileCheck %s -input-file=cfg.foo.dot --check-prefix=CHECK
+; RUN: rm -rf %t
+; RUN: mkdir -p %t
+; RUN: opt < %s -passes=dot-cfg -cfg-dot-filename-prefix=%t/cfg 2>/dev/null > /dev/null
+; RUN: FileCheck %s -input-file=%t/cfg.foo.dot --check-prefix=CHECK
 
 define void @foo(ptr %A, ptr %B) {
 a_very_long_label_that_should_take_over_eight_symbols_and_span_2_lines_in_cfg_dot_graph: